"IAP only works if you nag or tell each user about it by locking them out of what they want."<p>This is hard for most developers to understand: you have to create a pain point as costly as the IAP upgrade for the users, or else they won't upgrade.<p>The cost of free should be in lack of necessary features, or in annoying notifications. Either way, paid or free, the user should be paying, or else you won't make any money.