[JoshTriplett]

I'd be willing to bet that the vast majority of ad-based apps (without IAP of some kind) make less than $0.50 lifetime revenue on average from 90+% of users. Some quick checking suggests that the median total revenue for most apps is close to $0. Most apps would probably win out if they said "turns out ads don't work, would you be willing to pay $0.99". Even if they lost users, they'd gain revenue.

Whenever an unsustainable free service comes out on HN, and it's something people actually want, there's often a comment saying "this seems unsustainable, so I don't think I can count on it; please let us pay you". The same thing applies to apps.

[fomine3]

I doubt lifetime revenue is less than $0.5 in general. I'd like to see statistics. Even if $0.5 is correct, do you think 1/2 of users pay $0.99? Looks like optimistic.