Cheating at what? If you sell me your house for $1 then have you "cheated" all the other house sellers? What have you accomplished by this "cheating"?

Libertarianism treats the market as a game when it suits (i.e. when other people are "cheating") and as a natural law the rest of the time (i.e. when other people want to change the already-artificial rules of the game via politics).

I don't quite follow why you're saying that, but as per my brief previous comment, I'm not saying it's a natural law, nor a game.

Sorry, I thought you were implicitly calling it as a game (which is IMO the correct and true view), since cheating can only happen in a game where there are established rules.

Not particularly; I think you can call almost anything a game if you like. But I don't think it's especially a game, nor a natural law.

I don't see why anyone would characterise some people choosing to spend and lose their money as "cheating".