Best way to sell a cell phone app game

What

Is this really a thing?

I know highly ranked up CoC bases are worth a few hundred dollars.

It depends on the game.

If you have to register a separate account for the game then you can just sell that account.

If the game is tied to your google/apple account itself you'd have to sell those accounts. And those accounts may be tied to a bunch of other shite, so that's complicated.