eBay to Amazon profit math: what a listing really earns after every cost

Short answer

Profit is what Amazon pays you, minus everything it cost to get the item to the point of sale, minus a small reserve for returns. Write each cost on its own line, every time. If you skip a line because it is usually small, you will eventually skip it on the one purchase where it is not.

Step 1: list every cost on the Amazon side

Start from the price the item sells for on Amazon today, not the highest price you have ever seen. Then take off what Amazon keeps.

• Referral fee. A percentage of the sale price that depends on the category. The 15% used below is an example only.
• Fulfillment fee, if Amazon ships it for you. It depends on size and weight.
• Other fees that apply to your account or item, such as storage or inbound charges.

Do not guess these. Amazon's own fee preview for your exact item gives the real numbers. If you sell the item already, the Fee Preview Report in Seller Central lists them.

Step 2: list every cost on the eBay side

The asking price is only the first line. Add everything you pay before the item is ready to send to a buyer.

• The eBay price (or your top bid).
• Shipping to you, which is often shown separately and easy to miss.
• Sales tax, if you pay it on the purchase.
• Prep: a label, a bag, a box, your time if you price it.
• Your share of shipping the unit to Amazon, if you use inbound shipping.

Step 3: add a returns reserve

Some items come back. Rather than treating a return as a surprise, set aside a small percentage of every sale in your sum. Choose the percentage from your own return history. The 3% below is invented. If you have no history yet, start higher and lower it as your data comes in.

Worked example: one listing, full sum

All numbers invented. A kit sells on Amazon for 120.00. An eBay listing asks 68.00 plus 9.50 shipping.

Invented example, US dollars

Amazon sale price           120.00
- referral fee (15%)         18.00
- fulfillment fee             6.20
= Amazon proceeds             95.80

eBay asking price             68.00
+ eBay shipping to you         9.50
+ sales tax                    0.00
+ prep                         1.50
+ inbound share                0.80
= your total cost             79.80

returns reserve (3%)           3.60

profit = 95.80 - 79.80 - 3.60 = 12.40
return = 12.40 / 79.80        = 15.5%

If you had stopped at the asking price, you would have seen 95.80 minus 68.00, which is 27.80. The honest number is less than half of that.

Worked example: how much a small change moves it

Same item, but the seller asks 60.00 instead of 68.00. Total cost falls to 71.80 and the profit rises to 20.40, a return of 28.4%. Eight dollars off the asking price raised the profit by about two thirds. That is why a fixed profit line matters: the same item can be a skip at one price and a buy at another.

Step 4: turn the sum around to get your highest price

Instead of checking one listing at a time, work backward from your line once per product. Say your line is a profit of at least 15.00 and a return of at least 20%. With the invented figures above, Amazon proceeds minus the returns reserve is 92.20.

1. For the profit minimum: total cost must be 92.20 - 15.00 = 77.20 or less.
2. For the return minimum: profit must be at least 20% of cost, so cost must be 92.20 / 1.20 = 76.83 or less.
3. The lower of the two wins: 76.83. Take off the fixed costs (9.50 + 1.50 + 0.80 = 11.80) and the highest eBay price is about 65.00.

Check at an asking price of 65.00
cost   = 65.00 + 11.80 = 76.80
profit = 92.20 - 76.80 = 15.40
return = 15.40 / 76.80 = about 20%

Write that 65.00 next to the product. Now any listing for it is a comparison of two numbers, with no new sum.

Step 5: keep the Amazon price current

Every number in the sum depends on the Amazon sale price, and that price moves. A highest price worked out from last month's Amazon price can send you to buy at a loss. Refresh your Amazon prices on a schedule, and re-run the backward sum for any product whose price changed.

Matching matters as much as math. A sum run against the wrong Amazon item is wrong however carefully you do it. See how to find eBay listings to flip on Amazon for matching and the step-by-step sourcing guide for the whole routine.

Where software takes over

Doing this sum for every new listing is the part to hand off. MarginPing does it for power tools and tool kits you already sell. You give it your list of products. It watches new eBay listings for them, matches by model number and by UPC when the listing has one, and works out estimated Amazon fees, profit and return against the Amazon price. It sends a Telegram message only when the listing clears your profit line.

Amazon prices and fee estimates refresh several times a day, and you do not need to connect an Amazon account. The estimates are not a guarantee: check the match and the listing yourself. It never buys, bids, or messages a seller.

MarginPing is in final testing and not open for signups yet. At launch: $100 a month for up to 20 products. Starts with a free 7-day trial, no card needed, when we open. See eBay to Amazon alerts for how the alerts are set up.

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