Consumable In App Purchases (IAP from this point on) are the worst power Apple has ever given developers. I’m not sure what they’re supposed to be used for since intermediary currency and real-world purchases are supposedly forbidden. When I think of how IAP are supposed to be used, I think of this:
Subscriptions for apps with server side components and one time feature unlocks for other apps are perfectly acceptable. Games charging for additional levels is perfectly acceptable. As soon as you make a purchase consumable, however, everything changes.
Non-consumable IAP are tied to an account. You can use that Instapaper subscription on your iPhone, iPod Touch, iPad, and iPad Jr all at the same time without paying an extra dime. The same goes for feature unlocks. Consumables, on the other hand, are tied to a device, and are non restorable if your device isn’t backed up (and of course restoring means full device restoring). I’ll admit that as a developer I have way more active devices on a single Apple ID (without bending rules for family members) than most so maybe I’m not the best person to talk about this, but I’m pretty sure people aren’t used to paying an occasional recurring $50 for a game.
It seems I’m not alone, however. Please read the tale of Cow Clicker.