Why every marketplace has a different seller fee stack
No two marketplaces keep the same slice of your sale, so a price that nets 30% on one can lose money on another.
Amazon charges an 8-15% referral fee by category (plus a $0.99 per-item close on the Individual plan), with FBA and storage billed separately. eBay layers a 13.25-15% final value fee on top of a $0.40 per-order fee.
Etsy stacks four charges — a $0.20 listing fee, 6.5% transaction, 3% + $0.25 payment processing, and optional 12-15% offsite ads.
Mercari has moved to a buyer-paid service fee model, while Poshmark keeps a flat $2.95 under $15 and 20% on anything $15 and up.
Storefront platforms like Shopify take 0% commission but bill a monthly plan plus 2.9% + $0.30 processing.
A seller fee calculator adds every layer into one effective take rate, which is the only number that lets you compare Amazon, eBay, Etsy, and Poshmark on equal footing before you list.
Working backward from a target margin to a list price
Most sellers set price by markup — 3x cost — then discover the platform quietly took a fifth of it.
The reliable method runs the other way: decide the net margin you need, then solve for the price that survives the fee stack.
A marketplace profit calculator does this by treating fees as a function of price, not of cost, which matters because commission and payment processing scale with what you charge while your cost of goods stays fixed.
Percentage fees inflate every dollar you add, but flat per-order fees ($0.40 on eBay, $0.25 on Etsy, $0.99 on Amazon media) punish cheap items hardest — a $6 item can surrender over 20% to fees before materials.
Enter your product cost, outbound shipping, packaging, and any ad spend, set the margin you want, and the pricing calculator returns the retail figure that clears it on that specific marketplace.
Repeat it per platform and the cheapest place to sell often changes with your price point.
Comparing platforms with the profit and fee calculators
The workflow is two steps. Start with the fee calculator to see the effective take rate on a single order across the marketplaces you are considering —
for a typical $50 item, Poshmark keeps around 20%, eBay roughly 13.25% plus $0.40, Etsy about 13-15% baseline, and Amazon 8-15% by category.
Then move to the profit calculator, which subtracts fees, payment processing, ads, cost of goods, and shipping to show real take-home per order, so a lower headline commission with heavier processing can still lose to a higher one.
These figures use each platform's published rate card: Amazon 8-15% referral, eBay 13.25-15% final value plus $0.40, Etsy $0.20 + 6.5% + 3% + $0.25, Poshmark 20% ($2.95 under $15), Mercari's current buyer-fee structure, and Shopify 2.9% + $0.30.
Rates change frequently and vary by category, country, and seller tier, so confirm the current numbers in each marketplace's own fee schedule before you commit to a price.