I think there is a miscommunication in "worth" between some of the posts here.

Definition 1. - your version "a worker is only "worth" $50/hour if there is a supply of people willing to pay them $50/hour."

Definition 2. "a worker is "worth" $50/hour if they add $50/hour value for the business." (who then goes on to pay the worker as little as possible, maybe only $5/hr)

Not sure which definition is "correct".