I've only found this "value for value" thing on nostr, never hear of it before.

The "win-win" condition is instead the basic principle of free market.

Voluntary exchanges are such that both parties profit.

If I give you 5 dollars, and you give me in exchange a steak, it's because I value your steak more than my 5 dollars, and because at the same time you value my 5 dollars more than your steak.

Hence, win-win.