I'm an android guy, but I bought an iPad recently, and I think the author's missing a huge chunk of the issue here: Design & Culture. There is a big, big difference between how Google & Apple handle paid-for purchases - on Android, you get a confirmation screen, you have to verify the purchase, and you get 24hrs to return it. On iOS, you press a button and the app starts downloading. It's almost frighteningly fast - no confirmation screen, no returns, Congrats, and enjoy your $10 app. Psychologically, these are very different experiences, and I think they push users to spend more on iOS than android.

There's also a difference in average price points and expected prices - the android is absolutely cheaper. I think this is partly because the iOS marketplace is more mature, partly because big companies are not totally committed to android yet ("Testing the Market" price, not "Making Money" price), and partly self-reinforcing.

Whatever the cause, though, it's just flat out Easier to spend more money on iOS, and I suspect THAT's why Android devs aren't making what iOS devs are.

Mind you, I think Google's model is more consumer-friendly, and I endorse that, but the flip side to that coin is that Devs aren't making as much money, and that might hurt the platform in the long run.