These puzzles need to be handcrafted and a UI built. So they could hire other people to do it or hire the person who already has it done and start monetizing immediately.
I sold an app once to a company in the same situation. Neither one of us had sold / bought an app before so they asked me how many hours it took to write and what my hourly rate was. Then they offered half the number I quoted, which I thought was fair.
They paid a lot less than it would have cost to rewrite and I made a lot more than if I had just kept it as a free hobby app.
