I was thinking about that too, and I recall a thread where someone said a good strategy is to release a paid app for iOS and an ad-supported free one for android. That said, top 100 best sold apps here and there being priced quite differently is quite interesting and counter-intuitive.

I wonder if perhaps it might be partly due to some nicely priced niche apps being better represented in (by definition more open) android market than in the iOS one. Not that I know of any or actually looked into it; plus, I doubt many such apps would get into the top 100.