It's not so much about 'worth' but fairness. How would you react if you discovered a coworker doing the same (or inferior) work got paid twice as much as you?

It's not so much about 'worth' but fairness. How would you react if you discovered a coworker doing the same (or inferior) work got paid twice as much as you? You might be getting paid a good above-market wage, but most in that position would become jealous and jaded over time. I don't see any way around that.