Defectors don’t have to be one of the contract participants. People are free to create new companies. Price-busting venture capital would be a whole industry if

Defectors don’t have to be one of the contract participants. People are free to create new companies. Price-busting venture capital would be a whole industry if price-fixing was legal. It doesn’t even have to happen very often; the counterfactual possibility of getting busted is enough to keep price fixes reasonable.