He doesn’t intend to make money off of the third party apps. If he did, he could have set a reasonable price. He wants to shut them down so he doesn’t have to worry about them and to force people on to their app. Few, if any, 3rd party apps will ever pay the advertised price, so it will be peanuts if not literally zero as a revenue stream. The strategy is to get all users on Reddit-owned properties, be it the website or app or whatever else they may come out with.
I actually like Mooncake.