FBA or FBM? A Cost-Based Comparison
With FBA (Fulfillment by Amazon) you send your products to Amazon’s warehouse; Amazon handles storage, shipping, returns and customer service. With FBM (Fulfillment by Merchant) the stock stays with you; you do the packing and shipping. Both are “correct” models — the question is which one leaves more money on which product.
Cost structures side by side
| Item | FBA | FBM |
|---|---|---|
| Referral fee | Yes (by category) | Yes (same rate) |
| Fulfillment | FBA fee (size/weight) | Your own carrier deal |
| Getting stock to the warehouse | Yes (inbound shipping) | None |
| Storage | Monthly + long-term fee | Your own warehouse / home |
| Packing & labor | Amazon does it | Your time or staff |
| Returns handling | Amazon manages (may be charged) | Shipping + operations on you |
| Prime badge | Automatic | Only via special programs |
Where FBA wins
- Small, light products: the fulfillment fee stays low and the Prime badge lifts conversion.
- Fast turnover: stock doesn’t sit in the warehouse, so storage fees don’t eat the margin.
- Scale: packing dozens of orders a day doesn’t scale with your time — it scales with Amazon.
Where FBM wins
- Large/heavy products: FBA fulfillment + storage fees balloon quickly; your own negotiated shipping can stay cheap.
- Slow movers: the long-term storage fee is a silent margin killer on FBA.
- Low volume / testing phase: you can probe the market without sending stock to a warehouse.
Same product, two models: a worked example
A rough comparison for a light product selling at $39.99 with a $14 product cost:
| Item | FBA | FBM |
|---|---|---|
| Sale price | +$39.99 | +$39.99 |
| Referral fee (%15) | −$6.00 | −$6.00 |
| Fulfillment | −$5.50 (FBA fee) | −$8.90 (own shipping) |
| Inbound to warehouse | −$1.20 | — |
| Packing/labor | — | −$0.60 |
| Product cost | −$14.00 | −$14.00 |
| Net profit | +$13.29 (%33) | +$10.49 (%26) |
On this product FBA leaves roughly 7 points more margin — before even counting the Prime badge’s effect on sales velocity. But run the same math for a bulky 5 kg product and the FBA fulfillment and storage items grow; the table often flips in FBM’s favor. The decision is made per product, not per model.
Decision checklist
- Look up the FBA fulfillment fee for the product’s size/weight class.
- Work out the cost of the same shipment with your own carrier (packing included).
- Estimate monthly sales velocity and add the storage time — if it’s slow, don’t forget the long-term fee.
- Account for the return rate in both models.
- Put the two scenarios’ net profit side by side; for the full calculation see the profit margin guide.
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