The FBA Prep Costs Quietly Eating Into Your Margin

A few cents, times a lot of units

Poly bagging, FNSKU labeling, bubble wrap, bundling, prep-center handling — each one individually looks like pocket change, often well under a dollar per unit. But a profit calculation that only accounts for product cost and Amazon's fees, and skips prep entirely, is quietly overstating margin on every single unit in the shipment.

Why it's easy to leave out

Product cost and referral fee are the two numbers every seller checks first, since they're the biggest and most obvious line items. Prep costs are smaller and more scattered — a few cents here for a poly bag, a bit more there for prep-center labor — which makes them easy to mentally round down to zero, even though added up across a shipment of hundreds of units they're a real, recurring cost.

In-house or outsourced, it still counts

Whether you prep units yourself or pay a third-party prep center a per-unit fee, the cost belongs in the same place: your true landed cost, right alongside product cost and inbound freight. A prep center's invoice makes this easy to track since it's itemized already; in-house prep is easier to underestimate because the cost is spread across materials and your own time rather than one clean invoice line.

Add it all up in one place

Our FBA Prep & Labeling Cost Calculator lets you list every prep line item for a shipment and see the true per-unit and per-shipment total — a number worth plugging straight into a profit or break-even calculator's cost field.