A trend indeed. You know what each of those stores charging 30% have in common?

They each come bundled with the OS on your device and have massive advantages over any competing stores (if they even allowed them to exist).

Since devices are so expensive and users tend to be loyal, [company] isn't going to see much increase in sales by lowering their fees. With no competition and no downward pressure on prices, they just pick the 'industry standard', effectively price fixing without true collusion.

I'm pretty sure this isn't ideal but I don't pretend to know the answers. Until then, I'll just be focusing on building my ideas as web apps. (Flutter apps, so I can release elsewhere if the terms are reasonable).