Instead of cutting it off, can you just add some ads on the page? Many will probably complain, leave 1 star reviews, and stop using the app, but in the meantime you'll make some money off the app (even the free version).

Whatever ethical issues inherent in profiting off scraped content have already been bypassed by asking for money, though any issues with the law could be a bigger concern.

After balking at payment, I have cut him off and asked that profits be donated to the Red Cross. We'll see, crazier things have happened.