Most sellers price forwards: look at what similar items sold for, list a little under, hope. That’s fine for finding the ceiling the market will pay. It tells you nothing about the floor, the price below which you’re paying for the privilege of packing a box. This guide is about the floor.
Start with every cost, not just the purchase
Write down, for one item, every dollar that leaves your pocket between buying it and the money landing in your bank:
- What you paid for it. Include the sales tax you paid at the thrift store or the shipping on the wholesale lot.
- The shipping label. Your actual cost, not what the buyer pays. A 1 lb parcel across the country is roughly $5 to $9 through discounted marketplace labels.
- Packaging. A poly mailer is about $0.15; a box, tape and tissue can be $1 or more. It’s small per item and very real over a hundred items.
- Platform fees. The marketplace’s percentage, charged on the order total including buyer-paid shipping on most platforms, plus any fixed fee.
- Payment processing, where it’s separate from the platform fee (PayPal, Stripe, Etsy).
The break-even calculator handles the fee arithmetic, which is the fiddly part: a fee that’s a percentage of the price changes the price you need, which changes the fee. It solves that loop to the cent.
A worked example
A thrifted denim jacket, to be sold on eBay with free shipping.
| Cost | Amount |
|---|---|
| Paid at the thrift store, with tax | $8.50 |
| Shipping label (1 lb, 2 oz) | $6.20 |
| Poly mailer and tape | $0.50 |
| Cash out before fees | $15.20 |
eBay takes 13.6% plus $0.40. To cover $15.20 of costs and eBay’s fee on the whole price, the break-even list price is:
$(15.20 + 0.40) ÷ (1 − 0.136) = $18.06$
List at $18.06 and you make exactly nothing. Every dollar above that is profit, minus 13.6% of it. To clear $15.00 profit, the calculator gives a list price of $35.42: fees of $5.22, costs of $15.20, and $15.00 for you.
Now compare with the market
If similar jackets sell for $35 to $45, the $35.42 floor is comfortable and you can price toward the top of the range. If they sell for $22, the floor tells you the honest answer: this jacket makes about $3.50 for perhaps twenty minutes of work, and it should probably go back on the rack next time.
That is the whole point of pricing backwards. The floor doesn’t tell you what to charge. It tells you which items to buy in the first place.
The three costs sellers forget
Your time. Photographing, measuring, listing, answering an offer, packing and a trip to the drop-off add up to fifteen to thirty minutes an item. Most full-time sellers set a minimum profit per item, often $10 to $15, rather than a minimum margin, because a 60% margin on a $5 item is $3 for the same half hour.
Returns and unsold stock. Not every item sells and not every buyer keeps what they bought. A common approach is to knock a percentage off expected profit at the sourcing stage, say 5% for returns and 10% for items that never sell, rather than trying to price it into each listing.
Fees on buyer-paid shipping. eBay, Mercari and Depop all charge their percentage on the shipping the buyer pays. If you charge $6 shipping on eBay, $0.82 of it is gone before you buy the label. Charging for shipping doesn’t make it free; it makes it 13.6% more expensive than it looks.
Margin or return on cost?
Two numbers matter, and they answer different questions.
- Margin is profit as a share of what the buyer paid. It tells you how much of each sale you keep. A 40% margin means $40 of a $100 sale is yours after everything.
- Return on cost is profit as a share of what you paid for the item. It tells you how hard your sourcing money worked. Thrift flips often show a 300% return on cost and a modest margin; retail arbitrage is the reverse.
The reseller profit calculator shows both. When you’re deciding what to buy, look at return on cost. When you’re deciding what to charge, look at margin.
A pricing checklist
- Know your break-even before you list, not after the sale.
- Price for the profit you want, then check the market, not the other way round.
- Include the label at your real cost, even if the buyer pays shipping somewhere else.
- Set a minimum profit per item and stop buying things that can’t reach it.
- Recheck the fee tables every few months. Platforms change them, and a 1% change is a 1% change in your margin.