I remember life before the iOS App Store. Mechanisms for delivering software on MacOS usually took a much larger cut than 30%. Heck, when Apple announced 30%, Amazon had to scramble and switch from keeping 70% to matching Apple's 30%. Amazon still keeps 70% if you price your ebook under $3, in fact, while Apple does not.
Your comment implies price-fixing, but history demonstrates competition, and Apple lowered the costs for everyone.
Seems like a fair competitive market. /s