Our formula to calculate the prices is the following:

((amazon_price)*profit_percentage + desired_profit) \ (1 - break_even).

The logic behind it is the fact that we pay fees & taxes on the final price we ask in ebay ((amazon_price)*profit_percentage + desired_profit).

So we need to take it into account and divide it by (1-break_even).

BTW, in our app, break_even == The estimated average payments for fees and taxes (eBay & Paypal fees, Amazon taxes)

Let's take an example:

amazon_price = 10$

desired_profit = 3$

break_even = 18%

(amazon_price + desired_profit) = 13$

(1 - break_even) = 0.82

eBay price = 13 \ 0.82 = 15.85$

When it will be bought by someone on eBay, you would pay 18% fees & taxes so we get 15.85$ * 0.82 = 13$.

10$ will go to amazon seller and you will get the 3$ as you set for the desired profit!