How much can an app patent earn?

There are no rules. There is no standard price in the patent market, and a patent may or may not be valuable. A patent is an invention protected by legal norms. An invention that submits a patent application to a national or regional examination and approval authority and, after passing the examination according to law, grants the patent applicant the exclusive right to invent within a specified time. We can't generally say how much an ordinary invention patent or utility model patent can sell.