In that case, only the transaction mattered, not the exchange of goods. The buyer and seller were the same person. Or they were two parties who'd agreed to retu

In that case, only the transaction mattered, not the exchange of goods. The buyer and seller were the same person. Or they were two parties who'd agreed to return the payment. In this case, the exchange of goods is crucial (for their fixed value equal to payment). And there's no prearrangement between buyer and seller. Different means to the same end.