Whenever there's a transaction, that means that both parties give a different value to whatever is exchanged. For example, when you buy a home, the buyer prefers the house to the money and the seller prefers the money to the house. If this wasn't the case, the transaction just wouldn't take place.

So transactions are the opposite of a zero-sum game, they are a win-win game, where both parties end up winning. Because value is subjective.