Ad hoc. P2P. Case by case. Whatever the traffic will bear. There is no standard.

That may be frustrating to hear, but there is no formula for equating one's own instance with somebody else's other than free market trading.

Fiat money sometimes handles this by having cost of living adjustments, wage and price controls, etc., but those are just lies that the public accepts until they don't.

Again, Bitcoin is just a payment protocol. It doesn't have any way to judge how much you should get.