OK, let's do the math here.
You have a Marvel Legend action figure that costs you, say, $16 shipped at wholesale.
You put it on Amazon for $20. That's what Hasbro says they cost, that's what they sell for at other stores.
It sells for $20 plus $4.49 shipping (a $24.49 sale).
Amazon takes the flat fee. $0.99.
Amazon takes 15% of $20. $3.00
Amazon takes the shipping fee. $0.45
Amazon's total take is $4.44.
$4.44 is 18% of the total sale. Alternatively, $3.99 is 20% of item price (because, ideally, shipping is a pass-through cost rather than a profit center).
Unfortunately for you, shipping on a product that size has a floor of about $6.45 (God help you if there's any real distance between you and the buyer).
$24.49 - $6.45 - $4.44 - $16.00 = -$2.40
So, Amazon took 18% and you took NEGATIVE 9%.
Now put that buyer in California.
$24.49 - $12.40 - $4.44 - $16.00 = -$8.35
Amazon still takes 18% but you take NEGATIVE 34%
In order for you to make a single cent of profit under the best conditions on a $20 item, your buy price has to be $13.59. This is the scenario where Amazon takes 18% and you take 1%.
In order for you to take 18%, just like Amazon does, your buy price has to be $9.16. Under the best case. In order to make it under the California scenario, subtract another $6.
To sell a $20 product cross country (because you have ZERO control on Amazon), you have to get it for $3.
Who the hell has an 85% margin?