This. Some people seem to be on the "Apple deserves a cut of 30% because they run the app store and 30% is reasonable etc." but what if tomorrow Apple just said

This. Some people seem to be on the "Apple deserves a cut of 30% because they run the app store and 30% is reasonable etc." but what if tomorrow Apple just said: "OK we've bumped up the 30% to 90%". The exact same set of arguments would follow. The users already own the phones so for the "market to adjust" to such changes would take years.