A few years ago I looked at the finances of a company that sells on Amazon (FBA). It was pretty astounding the number of fees they charge. They were paying to show up in sponsored results which obviously increased the fees but from what I remember between all the fees roughly 50% of the sale price of their products was just going directly to Amazon.
Compared to the wholesale -> retail markup for most goods 50% is pretty in line with what a normal store would take as their cut, maybe slightly better.
Their margin is Bezos' opportunity. I don't know how he could have been more direct.
The endgame of capitalism is a big corporation with a nested market which is completely regulated to death by that big corporation.
Logistics and shipping cost a lot. Amazon is one of the cheapest warehouses that you can use for this purpose.