Is the App Store actually profitable for developers?

The App Store has been seen as one of vast opportunities for indie developers, giving the likes of Halfbrick, Firemint and Rovio a platform to release games on they might not have had by sticking to “conventional” consoles.

But is it really a happy marketplace? If we have a look on Game Center, it would seem that all but the very highest profile games do, in fact, struggle to make any real money.