[MatthewPhillips]

I don't particularly care if Marco makes an Android app, it's his product, his time, he should do what he wants.

But let's assume that his analysis (as biased as it is) is correct. It still might be a net positive to make an Android version if you consider this. All Android sales are potentially a double sale. Android has a majority market share on phones and iPad has a (overwhelming) majority market share in tablets.

There is a strong chance that the person buying his Android version would also have an iPad. This is pretty obvious when you think about it. Android covers a wide spectrum, with a lot of people on the low end. The people who would be buying his app must represent those on the high end (simply because they'll pay for it), and those people are far more likely to also have an iPad.

[batista]

All Android sales are potentially a double sale.

If the app-making was free. You forgot the "opportunity cost".

Android has a majority market share on phones and iPad has a (overwhelming) majority market share in tablets.

Yes, but does Android have a majority market share on apps sold? From what I have heard, I don't think so.

They just have a majority market share in phones because even people who don't care about a smart phone or apps get an Android phone for free with their contract. Whereas iPhone users are more picky in general about the phone they get, and more prone to fork out for apps. (Notice how I said "in general" --nerds are a small minority of smart phone buyers).