On iOS, 13% of Hero Project’s revenue has come from IAP. 9.4% of Zombies’ iOS revenue is from IAP (which only has one IAP, and was post-release).
The problem with Romance is that the bonus-IAP can’t be easily distinguished from the content-IAP, so there’s no valuable measure there.
But, if there’s a 10% boost to revenue due to IAP, I’d say that’s something to continue to feed. Not to focus on (eg we’re not switching to a freemium model, where you have to buy IAP to advance), but to feed.
I think the rest of COG would agree that our games will be complete in and of themselves. Though, I will admit, I have been encouraging (outside) authors to think about IAP as they’re writing/developing their games. The Hero Project’s IAP is the first fruit of that effort.