Earlier quoted context omitted.
How can you argue that it's not worth "anywhere near 10%, let alone 30%" if there are so many firms willing to pay it? The idea of the fees is not to cover the costs of doing business, it's to turn a (ideally significant) profit. It sounds like your expectation is that a company would not charge as much as the market will accept for a unique product. How much it costs to simply handle e.g. payment processing has rela…
The inverse question is equally interesting: In a monopoly, how do you determine when to put a stop to it? It's a tough question.
I expect that will be a pretty controversial opinion, but I'm just being honest.