I think the norm that everyone seems to slowly be settling on, of 15% for: 1) hosting the program itself, 2) displaying in the store, 3) payments and subscriptions including figuring out local taxes and CC fees and such, 4) various other services (push messages, for example), is pretty damn reasonable. 30% is clearly too high, but somewhere around 20% it actually starts to look like not-a-rip-off.