The App Store wasn't the first online store on mobile phones, there were stores for downloading ringtones and wallpapers on some devices and some primitive app stores particularly in Japan. The typical markup on these was 50% at the time, while typical retail markup is 40% for many types of goods. Consensus among pundits was that Apple would charge 50% and 30% was widely reported at the time as being surprisingly low.
Not to forget the 50% that telecom providers would demand for premium SMS / MMS (with one "chat" message costing 5€, half of it would get to the network provider). Which also explains why they had little incentive to prevent predatory services like SMS spam telling people to call / message high priced service numbers with subscription keywords.
