Yes, it is really astonishing. Even simple casual games like "Angry Birds" (http://de.wikipedia.org/wiki/Angry_Birds) sold 10 million units only on iPhone and are now available for Android, Symbian and Windows and are told to be converted to consoles too. Something like this is a money printing machine.

But this works only in the beginning that way. Later it will be harder. There will be more good titles and only the ones with a good advertising budget will sell that much.