Buying in Case Packs, Selling in Units: The Split Problem

By Bernardo Campelo, Forbes Business Council E-Commerce Leader and Founder of PrepVia, an Amazon SPN Certified prep center.

A distributor's case pack of twenty-four units at six dollars and ten cents a unit landed, almost a full dollar under the previous vendor, looks like a deal worth signing the same afternoon. The margin problem shows up weeks later, when that inventory reaches a receiving dock, because nobody in that negotiation priced what it costs to turn one sealed case into twenty-four units Amazon will actually accept.

The same gap sits inside almost every wholesale purchase order. The buyer negotiates hard on the number printed on the case, the price per unit at case pack quantity, and that number is real. What the purchase order never shows is a second number: the cost of opening that case, counting what is actually inside it against what the label claims, labeling every unit for Amazon, repackaging it into a carton Amazon will accept, and absorbing whatever units are left over when the case size does not match the shipment plan.

The price on the purchase order is the price of the case. The price that determines your margin is the price of the unit once the case is open, and those two numbers are rarely close.

Why Distributors Sell by the Case, and Amazon Wants the Unit

Distributors and wholesalers sell in case packs for reasons that have nothing to do with your Amazon listing. A case of twelve, twenty-four, or thirty-six units is a manufacturing and freight decision made long before your purchase order existed. The case configuration matches a carton that fills a pallet efficiently, ships a full truckload without wasted cube, and moves through the distributor's own warehouse as one countable unit instead of loose pieces. None of that logic considers what Amazon needs from you.

Amazon, in most categories, sells one unit at a time. The ASIN a customer buys is a single unit, and unless your case itself is registered and listed as its own multi-pack ASIN, a narrower situation covered later in this piece, Amazon expects to receive and fulfill individual units, each carrying its own scannable barcode. That mismatch, a supplier selling by the case and a marketplace selling by the unit, is the entire split problem. It exists on every wholesale deal, and almost nobody prices it before the purchase order is signed.

A buyer sourcing by the case pack and selling by the unit needs a receiving process that counts, labels, and repacks at case-breaking speed, not a generic receiving dock built for a brand owner shipping their own single-SKU cartons. That is the gap a wholesale and distributor prep workflow has to close.

What Breaking a Case Actually Requires

Breaking a case sounds like one task. It is four, and each one carries its own labor and its own chance to go wrong.

The Four Steps Nobody Prices on the Purchase Order

Each of those four steps is real labor, and on a case of twenty-four to thirty-six units it is not fast labor. A prep team working a single case has to touch every unit inside it at least twice, once to inspect and count, once to label, before repacking even starts. FNSKU labeling alone is usually the fastest of the four steps. Verification and repacking take longer, and neither one shows up as a line on the supplier's case pack quote. Our guide to FNSKU labeling for FBA covers what that single step involves in more detail.

The Master Carton Becomes Waste the Moment You Open It

The case the distributor shipped you was built to survive a pallet, a truck, and a warehouse shelf. It was not built to survive being opened, and it is almost never built to satisfy Amazon's carton requirements once it is opened either.

Most master cartons carry the distributor's own branding, a case count printed on the outside, and dimensions sized for the full case rather than for a partial or reconfigured shipment. Once the case is cut open to pull units for labeling, that carton loses its structural integrity at the seam and often cannot be resealed to Amazon's box requirements, which call for a rigid, six-sided box with flaps intact. The units that come out of it need a new outbound carton, sized and rated for whatever quantity is actually shipping in it, sourced and paid for separately from anything on the original purchase order.

That is a real material cost, not a theoretical one, and it sits on top of the labeling and poly bagging lines a case-broken shipment already carries. It is also, less obviously, a waste stream. A pallet of twenty broken cases produces twenty master cartons that are rarely fit to reuse, and most of them go straight into the recycling bin at the prep facility, which is one more reason the intact case, when it is an option, deserves a second look before you assume breaking it is the only path.

The Leftover Problem: When the Case Does Not Divide Into the Shipment

Case math and shipment math rarely line up on their own, and when they do not, the mismatch produces orphaned inventory that sits in storage with no shipment to join.

Say a shipment plan calls for five hundred units, and the case pack size is twenty-four. Five hundred divided by twenty-four is twenty full cases, four hundred eighty units, with twenty units left over. Those twenty units have to come from somewhere, which means a twenty-first case gets opened for a partial pull, and four units from that case now have no home in this shipment. They sit in storage until the next shipment plan needs them, if it ever calls for that exact SKU again in a quantity that uses them up.

That leftover is not free. Storage is billed on the space used, often daily, and four units of almost any physical product occupy real space for as long as they sit unclaimed. A handful of units at a low daily rate looks trivial on any single invoice. Multiply it across every SKU in a wholesale catalog where case size and shipment quantity rarely align, and the orphaned inventory becomes a real, recurring storage line a purchase order priced purely on unit cost never accounted for. Our guide on how many units to send in a first FBA shipment covers the sizing side of this problem in more depth.

The Case Pack Math: Intact vs. Broken, Same Purchase Cost

Here is the same product, the same purchase cost, run two ways, so the split cost stops being an abstract idea and becomes a number you can check against your own catalog.

The item is the case from the opening of this piece: a single SKU bought at $6.10 a unit landed, packed twenty-four to a case, needing a poly bag under Amazon's prep rules, with a suffocation warning on the bag, once it ships as a single unit. The table below compares that same case two ways: shipped and sold intact as its own multi-pack listing, versus broken down and sold as twenty-four individual FBA units.

The purchase cost never moved. It is $6.10 a unit either way, exactly what the distributor quoted at the top of this piece. What moved is everything downstream of that purchase: on this item, breaking the case adds four per-unit lines (labeling, a poly bag, case break handling, and a replacement carton) that the intact case does not carry. On a thin-margin wholesale SKU, that is the difference between a deal that pencils and one that does not, and it never appears anywhere on the supplier's case pack quote. PrepVia pricing is quoted per account on a free 15-minute call, so get a quote and run your own SKU through the same math before you sign a purchase order.

When Keeping the Case Intact Is Worth the Higher FBA Fee

Breaking the case is not always the right move, even though it is the default assumption for most single-unit ASINs. There are real situations where paying Amazon's higher per-unit fulfillment fee on an intact case beats the split cost by a wide margin.

Two Situations That Change the Math

The clearest case is a product that can legitimately be listed and sold as its own multi-pack ASIN. If a case of twenty-four is also a sellable configuration, a value pack or a case deal a customer would actually buy as one unit, then it never needs to be broken at all. It ships intact, it carries one label instead of twenty-four, and the entire split cost in the table above disappears. Amazon's per-unit fulfillment fee on a larger, heavier multi-pack is usually higher than the fee on a single small unit, and that fee difference should be checked against the SKU's own fulfillment fee before assuming, but on many products it is still cheaper than paying to open, label, and repack every case by hand. Our breakdown of how Amazon's inbound placement fee works is worth reading alongside this decision, because the fee works the opposite way many sellers assume. Amazon-optimized splits, which send inventory to five or more locations, cost nothing, and the fee is charged when you choose minimal splits to ship to fewer destinations. Intact cases help you qualify for the free option, because it requires at least five identical cartons or pallets per item, same quantity and same mix in each.

The second situation is a low-margin SKU where the added split cost from the example above would erase most of the profit on the unit. If breaking the case turns a two-dollar margin into a much thinner one, the math is telling you something before you sign the purchase order, not after. That signal should change the negotiation itself. Ask the distributor for a smaller case pack size, six or twelve instead of twenty-four or thirty-six, which shrinks the leftover math from the earlier section and reduces how much labor a broken case actually requires per unit shipped.

The Rule of Thumb: When to Break a Case and When Not To

None of this requires a spreadsheet for every SKU. It requires one comparison, made once per product, before the purchase order gets signed instead of after the inventory is sitting in receiving.

The purchase order price and the shipped price are only the same number when the case ships intact. The moment it has to be broken, the real per-unit cost is whatever the split adds, and that number belongs in your margin calculation before the deal closes, not after the first invoice from the prep center arrives.

Frequently Asked Questions

What does it actually cost to break a case pack for FBA?

On a typical case of twenty-four units, breaking it into single-unit FBA inventory adds four per-unit lines on top of whatever the purchase price already was: FNSKU labeling, poly bagging where required, case break handling, and replacement outbound cartons. The exact number depends on whether the product needs a poly bag and how the receiving facility bills case break handling, so run your own SKU through the math in this piece before assuming a flat percentage.

Why can I not just reuse the original master carton to ship to Amazon?

The master carton is built to survive a sealed pallet, not to be reopened and resealed, and cutting it open at the seam to pull units usually destroys the structural rating a shipping carton needs. Most master cartons also carry the distributor's branding and a case count printed for the full case, not for whatever partial quantity ends up shipping to Amazon, so a new outbound carton sized and rated for the actual shipment is usually required once the original case is opened.

What happens to the leftover units when a case does not divide evenly into my shipment plan?

The extra units from a partially opened case have no shipment to join and sit in storage, billed on the space they use, until a future shipment plan calls for that exact SKU in a quantity that uses them up. On a single SKU a few orphaned units look trivial, but across a wholesale catalog where case sizes and shipment quantities rarely align, the storage cost from leftover units becomes a recurring line a purchase order priced only on unit cost never accounts for.

When does it make sense to keep a case pack intact instead of breaking it?

Keep the case intact when it can legitimately be listed and sold as its own multi-pack ASIN, because then it never needs labeling, poly bagging, or repacking as individual units at all, only a higher per-unit Amazon fulfillment fee that is often still cheaper than the split cost. It also makes sense to negotiate a smaller case pack size with the distributor when the split cost on a broken case would erase most of a thin-margin SKU's profit, rather than absorbing that cost silently on every reorder.

Does breaking a case pack always require a new FNSKU label on every unit?

Yes, when the item ships and sells as an individual-unit ASIN, Amazon requires a scannable FNSKU on every unit regardless of how it arrived, and a case-level barcode that covered the sealed case does not carry over to the individual units inside it. The only way to avoid labeling each unit is to keep the case sealed and sell it as its own multi-pack listing, which is a different product configuration entirely, not a shortcut around single-unit labeling.

How do I calculate my real per-unit cost before agreeing to a case pack deal?

Start with the purchase price per unit at case pack quantity, then add FNSKU labeling, any required poly bagging or shrink wrap, a market rate for case break handling and unit verification, and replacement outbound carton materials, using the worked example in this piece as a template. Compare that fully loaded number, not the purchase order price alone, against your target margin before you sign, because the purchase order number is only the starting point of what the unit actually costs you.

Is a case break handling fee a legitimate prep center charge or a hidden fee?

It is a legitimate charge for real labor (opening, counting, and verifying a sealed case) before any labeling begins, and it should appear as its own line on an invoice rather than being folded into a generic prep charge. The problem is a purchase order or a quote that never mentions it, which is why asking what a case break actually costs before you sign matters as much as asking the per-unit prep rate.

Final Take

The deal at the top of this piece is not a bad deal. Six dollars and ten cents a unit is a fair landed cost for that product. What makes it a problem is a negotiation that stops at the case price and never continues into what it costs to turn that case into sellable Amazon inventory.

That gap is the default shape of almost every wholesale purchase order, because the person quoting you a case price is pricing their own cost structure (freight, warehousing, manufacturing runs), not yours. The moment that case crosses into your operation and has to become individual units on an Amazon shelf, a second cost structure starts, and it belongs to you alone.

Pricing that second cost structure before you sign comes down to four steps, a carton you will probably throw away, and a leftover math problem that either divides evenly or does not. Run those numbers once per SKU, the same way the worked example in this piece runs them, and the case pack price on the purchase order stops being a number you hope holds up and starts being a number you already know does.

If you are buying by the case and selling by the unit as a regular part of your business, that math is worth building into how you evaluate every new supplier deal, not just the ones that already went wrong. Our wholesale FBA prep workflow covers how that receiving and labeling process actually runs once the purchase order becomes inventory in a warehouse.