My own iPhone photo app, Liquid Lens:
https://itunes.apple.com/us/app/liquid-lens-real-time-psyche...
actually briefly cracked the top 200 photo apps this month and pulls in more than $90 but is still only in the coffee money income bracket.
After four years of the indie iOS thing I'm tooling back up to do web dev again.
So far this hasn't been true though. Currently IAP revenue from the free version tends to be about 1/3 the revenue of the paid version even though free app downloads outnumber paid by at least 10 to 1 on most days. It does seem like IAP has been ticking up a bit over the last few weeks though. Maybe people have to play with the app for a while before they're willing to pay for it?
Personally I'd prefer to just do paid apps, since adding IAP + store transactions adds a fair bit of work.