Everything not just money. A marriage is a consistent exchange of value for example. Both parties gain and lose at various times. But they remain in the relationship based on their subjective valuations of what the relationship provides. And they leave the relationship when their subjective valuations suggest they’d be better off with an alternative.

Also it doesn’t have to be a strong relationship. You still have a “relationship” with Amazon when you buy something online. You are a customer. But the relationship ends the moment the transaction is complete. But before the transaction is complete, you are determine what value this entity can provide for you. You do the same thing when you are dating. You determine what this woman can provide for you and you try to see if what you offer is something she wants. It’s all economics 😂