There's precious few mobile games that I've actually spent money on.
Think I've chucked about £1.40 at the makers of Cut The Rope, £0.70 for Sprinkle Jr., but that's about it. In-app purchases just strike me as a rip off - if the game is good, I would buy it, but the App-Stores seem to function on quantity over quality, so I just assume that everything will be shit* and play the free versions, chucking them once I reach the point where I need to pay to progress.
*Experience shows this to generally be the case, most mobile games are either outright dire, or get very dull, very quickly. Plenty of money being made, though, so someone must be hurling their cash at this crap.