You pay a final value fee
You pay a commission (depends on category and price realized, but usually in the 12-13% range)
You pay a commission on shipping
You pay a commission on sales tax and other taxes they collect

It's never 35%, but if you sell a low-priced item for a dollar or two with high shipping and sales taxes, it will seem that it is 35% of the item price. But that's not the calculation.