A prep center quote almost always leads with one number. Forty-five cents a unit. Thirty-five if you commit to volume. It is the number in the email subject line, the number on the pricing page, and the number sellers put side by side in a spreadsheet when they are choosing between three operators.
It is also, on most invoices, one of the smaller lines.
The per-unit prep rate is the easiest number to compare, which is exactly why it gets compared. Everything else on the invoice — receiving, storage, outbound, and the fees that only appear once you are already shipping — is quoted in different units by every operator, so it resists comparison and gets skipped. That is where the money is.
This is a walk through the whole invoice: what each line pays for, where operators differ, and how to turn four incompatible quotes into one number you can actually rank.
The invoice has five lines, not one
Every prep center bills some version of the same five buckets, no matter what their pricing page looks like:
Receiving — getting your freight off the truck and into their system
Prep and handling — the per-unit work: labels, bags, bundles, inspection
Storage — holding your goods between arrival and departure
Outbound — building the shipment that goes to Amazon or your customer
Exceptions — everything that happens when reality does not match the plan
An operator quoting "45¢ all-in" has folded three or four of these into one rate. An operator quoting "22¢ per unit" has almost certainly unbundled them. Neither is dishonest. But you cannot compare them until you have pushed both back into the same five buckets.
Line 1: receiving
Receiving is billed per carton, per pallet, or per unit, and the choice matters enormously depending on how your goods arrive.
Per-carton receiving is the most common and the most dangerous for small-carton products. If your supplier packs 12 units to a master carton and you are paying $7 a carton to receive, you are paying 58¢ a unit before anyone has touched a label. The same product packed 48 to a carton costs you 15¢. Your case pack, which you probably negotiated on freight grounds or not at all, is quietly setting your receiving cost.
Things to pin down before you sign:
What counts as a carton. Some operators bill the master carton, some bill every inner box they open.
Floor-loaded vs palletized. A container that arrives floor-loaded takes hours to unload by hand. Most operators charge a separate unload fee for it, often per container or per hour, and it is rarely on the pricing page.
Whether receiving includes a count. A piece count against your packing list is real labor. If it is not in the receiving fee, it is either not happening or it is a line item you have not seen yet.
What happens on a discrepancy. If the count is short, do they stop and email you, or do they receive what is there and move on? Stopping is correct and it is also billable time.
Line 2: prep and handling
This is the headline rate, and the only question that matters is what is inside it.
A "base prep" rate almost always covers an FNSKU label applied to a unit that needs nothing else. That is the cheapest possible unit of work and very few real products qualify. Ask specifically which of these are included and which are à la carte:
Polybagging, and whether the bag is included or billed as a material
Suffocation warning labels on bags with a five-inch-plus opening
Bundling and multipack assembly, which is usually billed per component, not per bundle
Removing or covering the manufacturer's barcode
Fragile or liquid overpacking
Expiration date printing on unit and carton
Photographing units on receipt, which good operators do by default and some bill for
Basic inspection — and "inspection" ranges from a glance at the carton to opening every unit
Materials deserve their own question. Bags, labels, tape, dunnage, and cartons are consumables, and some operators bill them at cost plus a markup while others fold them into the prep rate. A 30¢ prep rate with 12¢ of materials on top is a 42¢ prep rate.
Then ask about the minimum. Many operators have a monthly minimum invoice — $250 and $500 are both common — which is irrelevant at 3,000 units a month and is your entire cost structure at 300.
Line 3: storage
Storage is billed by pallet position, by cubic foot, or by bin, and the unit of measure is worth more attention than the rate.
Pallet-position pricing is simple and punishes low-density goods. If your product fills a third of a pallet, you are paying for a full position. Cubic-foot pricing is fairer for oddly shaped inventory and harder to forecast. Bin pricing suits small, high-value units and gets expensive at volume.
Three details change the total more than the rate does:
The billing cycle. Calendar-month billing charges you for a full month whether goods arrive on the 2nd or the 29th. Anniversary billing charges from the day goods land. If you turn inventory fast and receive mid-month, calendar billing can double your effective storage cost.
Whether it is prorated. Some operators bill a full month per pallet regardless of when it leaves. Goods that sit eight days cost the same as goods that sit thirty.
Free storage windows. A common and genuinely valuable term is 14 or 30 days free from receipt, after which storage begins. If your goods normally clear in under three weeks, an operator with 30 free days effectively has zero storage cost for you, and their higher headline rate is irrelevant.
Ask how they measure occupancy — daily average, month-end snapshot, or peak. A month-end snapshot rewards you for shipping out before the last day and penalizes you for receiving on it.
Line 4: outbound
Outbound is where per-unit thinking breaks down, because the work scales with boxes and shipments, not units.
The line items to expect:
Shipment plan creation in Seller Central, sometimes per plan and sometimes per destination the plan splits into
Box packing and labeling — per outbound box, including the FBA box label
Pallet building, wrapping and labeling for LTL shipments, per pallet
Carrier handoff or BOL preparation, occasionally separate
Freight, if they book it, and whether they mark it up or pass it through at cost
Amazon splitting one plan into three destinations turns one shipment into three sets of box labels, three pickups, and often three plan fees. Ask directly: when Amazon splits a plan, does the per-shipment fee multiply? For sellers running frequent small replenishments, this line quietly becomes the largest one on the invoice.
If the operator books freight, ask for the markup as a number. "We get better rates than you can" may be true and is not an answer.
Line 5: the exception fees
These never appear in the quote and always appear on the invoice. Ask about each one before you sign, because asking afterward means negotiating from inside.
Rework and relabel, usually hourly, for when Amazon's requirements change or a label was wrong
Removal orders and returns processing, per unit, and this one is often expensive
Disposal, per unit or per pallet
Long-term storage penalties on their side, separate from Amazon's
Rush or same-day handling
Special projects, the hourly rate that covers anything not on the price list
Account or platform fees, monthly, for the portal
Exit fees — pulling your inventory out, per pallet or per unit, and this is the one that traps people
Get the hourly rate in writing. It is the fee you will meet most often and the one least likely to be quoted.
The number that actually matters
Blended cost per unit shipped. Take everything the operator would have billed you last month, divide by the units that left the building. That is the only number that compares two quotes honestly.
Run it against your own real numbers: your case pack, your monthly volume, your turn rate, your shipment frequency. Not the operator's example.
Two quotes, worked out
Say you move 1,200 units a month. Case pack is 24, so 50 cartons in and 50 boxes out. You ship to Amazon four times a month in batches of 300, and you average three pallets on hand. These figures are illustrative — the point is the shape, not the rates.
Operator A — the cheap-looking one:
Prep at 40¢ × 1,200 = $480
Receiving at $8 per carton × 50 = $400
Storage at $22 per pallet × 3 = $66
Outbound boxes at $5 × 50 = $250
Shipment plans at $25 × 4 = $100
Total: $1,296, or $1.08 per unit
Operator B — the expensive-looking one, all-in at 65¢ covering receiving, prep, box packing and plans:
Prep at 65¢ × 1,200 = $780
Storage at $30 per pallet × 3 = $90
Total: $870, or 72.5¢ per unit
The operator quoting 65¢ is 33% cheaper than the one quoting 40¢. On this volume that is $426 a month, or roughly $5,100 a year, decided entirely by line items nobody put in the comparison spreadsheet.
Flip the assumptions and the answer flips. Double the case pack to 48 and Operator A's receiving halves to $200, closing most of the gap. Ship once a month instead of four times and A's plan fees drop to $25. The winner depends on your case pack and your shipment cadence, which is precisely why a generic "cheapest prep center" list is useless and your own spreadsheet is not.
What location does to the total
Two costs sit outside the prep invoice and are decided by where the prep center is.
Inbound freight from the port to the facility. A prep center 40 miles from the port your goods land at is materially cheaper to feed than one three states inland, and drayage is priced steeply enough to swamp a few cents of prep rate.
Outbound distance to the fulfillment centers Amazon assigns you. Placement is not something you control, but proximity to a dense cluster of nodes shortens transit, cuts LTL cost, and shortens the gap between goods leaving the prep center and units going live.
There is a third consideration that is not a freight cost at all: holding inventory in a state can create sales tax nexus. That is a question for your accountant, not your 3PL, but it belongs on the list before you pick a state.
We worked that decision through state by state in where should your prep center be, which sets the sales-tax-free states against the port states and links into the catalog for each one.
Making quotes comparable
The fix is to stop asking for pricing and start asking for a quote against a fixed scenario. Send every operator the same brief:
Monthly volume, units per master carton, arrival format (palletized or floor-loaded), prep required per unit, average days on hand, shipments per month, average boxes per shipment, and whether you need pallets. Ask for a total monthly estimate against those numbers, itemized by the five buckets, plus the exception rate sheet.
An operator who returns an itemized total is one you can work with. An operator who returns "45¢ per unit, contact us for details" has told you something useful too.
Keep the brief identical across every operator you approach, including case pack and shipment cadence. The moment one quote is priced against different assumptions, the comparison is gone and you will not notice it is gone.
Before you sign
The vetting checklist covers whether an operator can do the work. This covers what the work costs. The two questions that connect them:
"Show me a real invoice from a client my size, with the names removed." An operator with clean pricing will do this. It surfaces every line item their quote left out, in the order they will actually appear.
"Which of these fees have you charged in the last three months, and how often?" Rates on a sheet are theory. Frequency is the cost.
Then re-run your blended per-unit number every quarter against the invoices you are actually getting. Case packs change, turn rates drift, Amazon splits more shipments than it used to, and the operator who was cheapest at 1,200 units a month is often not the cheapest at 4,000.
To collect the quotes themselves, browse prep centers by state and service, run the shortlist through the 20-point due diligence checklist, or start a request and have prep centers price your scenario directly.
