How to compare FBA and FBM properly
The comparison is not "which is cheaper per unit" — it is which leaves more profit after every cost that differs between the two. The referral fee is identical either way, so it is not part of the decision. What differs:
A worked example
A 2 lb product selling at $34.99 in a 15% referral category, costing $11.00 landed:
FBA wins by $3.21 a unit here — because Amazon's negotiated shipping rates beat retail parcel rates on a 2 lb package. That advantage narrows as products get heavier and bulkier, and it reverses entirely on oversize items.
Where each model actually wins
The costs sellers leave out of FBM
FBM looks cheaper than it is because most comparisons only count postage. The full picture also includes:
- Your time. Picking, packing and dropping off has a real hourly cost. At 30 units a day it is a part-time job.
- Packaging materials. Boxes, mailers, tape, labels and dunnage.
- Storage. Space at home or a warehouse is not free just because the invoice is not from Amazon.
- Returns handling. You process every one yourself.
- Performance risk. Late shipments and tracking failures affect account health in a way FBA does not.
The costs sellers leave out of FBA
- Inbound freight and prep to get units into the network in the first place.
- Inbound placement fees if you do not use Amazon-optimized splits.
- Peak-season storage, roughly three times the off-peak rate in Q4.
- Aged inventory surcharges on anything that stops selling.
- Removal or disposal fees when you eventually clear it out.
Most established sellers run both — FBA for fast movers, FBM for heavy, slow or seasonal stock. The decision belongs at the SKU level, not the account level, and it is worth revisiting whenever Amazon changes its fee schedule. SellerGuards tracks FBA and FBM orders side by side with their own costs, so the comparison stays live rather than a one-off calculation.