Re: I learned something
Where have you been? All the big app stores take 30%, Apple and Amazon included. Apple has set the pace by taking 30% since the beginning of the App Store; the others have just followed. It's slowly changing though: Microsoft also takes 30% for games, but starting from this year, they only take 15% for other apps. Google has also reduced some of their fees to 15%.
I've heard the argument that it would also cost developers a lot to maintain their own website and payment systems. And in a sense, it's because the app stores exist that users are not just copying every single app under the sky without paying. That said, it does seem that the percentages are going down, so the app stores might have realized they are charging too much.