There are two classes of people: people who want to pay you, and people who don't.
Consider focusing all your attention on people who want to pay you. How can you make it really easy for them to pay? What do they want, and how can you do more of that for them? How do you find more people who want to pay you, how do you let them know you exist? Is your app so great that the people who want to pay you are telling their friends who want to pay you?
People who don't want to pay you don't make any difference whether they're using your service or not (you're not getting any money from them either way), unless there are so many of them that it's costing you something in server load or your time, in which case you can do something about it based in the specific pattern of abuse that you're getting.
It think that trying to force people who don't want to pay you to pay you is probably wasted effort, they'll just go away and not pay someone else :-)
