It's not just my definition of fair wage, it's the insight that "fair" can only be determined by the parties involved in the transaction, providing they have ad

It's not just my definition of fair wage, it's the insight that "fair" can only be determined by the parties involved in the transaction, providing they have adequate information such as minimum and market wages for their craft, the value created by their effort, etc. This is the key insight that OP is missing which makes them incorrectly think that "fair" can never be determined because it is some kind of objective goal post. It's not, it's highly subjective and local.