Manipulation is the right tool for a one-off transaction; the case against it holds only where repeated dealing is wanted.

The claim

Manipulation is the right tool for a single transaction. Where the parties will deal once, there is no relationship to build, and paying for the one act (a reward, a discount, a sharp offer) is cheaper than earning loyalty. The argument against manipulation therefore holds only where repeated dealing is wanted; a business whose customers come once can rationally invest in the transaction and not in loyalty. The case offered is a gold-buying service that stopped trying to be better than rivals once it found almost every customer used it only once, and became more profitable.