Your situation isn't everyone's situation though. Yes, 30% seems more reasonable if you're starting from scratch and don't want to set up all of that stuff yourself, but what about the businesses that already do business outside of the app store, that have their own marketing and payment processing, run their own servers, operate in different markets, etc? They may not have 30% in their margins to spare for a services bundle that they largely don't need.
If all you want is to be listed in the app store (because there's no other way onto people's phones) and some form of payment processing (because Apple doesn't let you use your own) for, say, a $5/month service that's runs on your own servers, then it absolutely is highway robbery.