Does this cartel punish defectors? How can it prevent people who don't want to participate from undercutting it? It doesn't, and it can't. That's what makes it

Does this cartel punish defectors? How can it prevent people who don't want to participate from undercutting it? It doesn't, and it can't. That's what makes it not a cartel. The problem is not collusion, the problem is supply shortage. All the sellers raising prices isn't illegal, or cartel-like. All the sellers punishing a seller that lowers prices would be - but it doesn't happen. Not with landlords, at least. I think our current land policy is pants-on-head stupid, but this isn't the problem with it.