Seller guide
How do I compare Amazon FBA vs FBM costs?
Build two honest seller-supplied cost stacks, compare per-unit and monthly contribution, and understand what the arithmetic cannot decide for you.
Use the same sale and product economics on both sides
Start each mode with the same SKU, sale price, product cost, referral rate, and monthly units. If those shared assumptions differ, the result mixes a pricing or demand scenario into the fulfillment comparison and the mode label stops answering the question you asked.
List variable costs without hiding inconvenient rows
For FBA, enter the fulfillment, inbound shipping, prep, labeling, storage, and other per-unit amounts you actually want to model. For FBM, enter pick-and-pack, packaging, outbound shipping, labor, and other variable costs. Use current seller-supplied figures rather than a generic fee table.
Allocate fixed costs across the comparison period
Software, warehouse space, equipment, and recurring service costs do not move one-for-one with units. Subtract each mode's fixed monthly costs after multiplying per-unit contribution by volume. A cheaper unit cost can still produce less monthly contribution when its fixed stack is larger.
Treat the higher-contribution mode as arithmetic, not a decision
A worksheet does not measure service levels, storage constraints, return handling, capacity, cash timing, seasonality, or operational risk unless you supply those effects as costs. Use the crossover calculation to see where the math changes, then review the omitted operational constraints before acting.
Tools that help with this
- Amazon FBA vs FBM Cost Comparison Worksheet ($0.50) — Compare up to 100 seller-supplied SKU cost stacks in an XLSX
- Marketplace Price Change Break-Even Analyzer ($0.25) — Stress-test the shared sale price and contribution assumptions
- Inventory Restock and Stockout Risk Planner ($0.25) — Review demand-only stock cover before changing fulfillment operations
Every paid output is a draft for your review before you publish, appeal, or activate anything. Friday does not access your seller account.