What does other digital distributors charge?
Steam, Desura, and GOG all charge in the neighborhood of 30% of the customers' purchase. Then there's Wolfire Games' Humble Store,
charging a gobsmackingly miniscule 5%. I'm a huge Desura fan, being a Linux gamer, but I must admit that Wolfire have done has been pretty amazing.
The whole Humble Store concept (modulo the THQ bundle) feels a lot like an indie development house decided one day to build something for themselves and their peers to alleviate common pain-points in sales & distribution (from what I've read, that's pretty much how it went down).