It costs money to publish an iOS app in a way that it does not for Android. In addition, the Android app was able to leverage the fact that Anki's desktop app is written in Java. It has nothing to do with an idea that "iOS users are rich". It is easy to recommend Ankiweb instead since it works well enough for mobile.

(I also question whether there are really a significant number of people who type -- at least Latin characters -- faster on mobile than a PC keyboard, but that's a digression)