That is currently the only thing they're charging for. Like I said, let them unbundle if they want to. I wouldn't be surprised if they actually end up just taking a revenue hit to keep the ecosystem healthy, which would mean more money for developers.
Thanks for making the distinction between when you are charged and why then charge is for.
Businesses rarely map charges directly into what is being paid for, because that doesn’t work in practice. Charges are made at a convenient point and then used to pay for the service as a whole. This is common practice across all kinds of business.
This matters because people are claiming they it is just for payment processing and then arguing that 30% is too much, which is clearly a dishonest position.