How much does an app patent cost?

Answer 1

Software (e.g. apps) are generally not patentable. They are covered under copyright law instead like other "works of art" (e.g. books, music, pictures, plays, movies).

Occasionally one or two unique algorithms in a piece of software that were supposedly never developed before can be patented as a "mechanization" or "process" but this is very rare and only covers that tiny algorithm, not the complete program.