Well I think it does exist. You can be happy with what you have regardless of what others have, can you not? Otherwise you're doomed to unhappiness, unfortunately.
> It's not illogical or irrational to not be happy with being paid less than you could be paid doing the same job
Agreed, it's not illogical or irrational, but it is sub-optimal if one is concerned with being happy with what they have rather than comparing against external entities and adjusting happiness downward unnecessarily.
> treat employees like fools
I don't think it's backward or disrespectful to ask someone what would make them happy and then give it to them.
I think it would be illogical to say "I want to make more than, or just as much as, anybody else doing what I do". Actually, I think maybe it's emotionally childish, rather than illogical. Not that I've never though that way myself. It's just that from a personal growth perspective, I don't think it's a mentality that leads to happiness in the long run.
This doesn't really exist. What people want is the most they can get, and this will make them as happy as is possible in the market. They would be as happy as anyone could possibly be about wages if they were offered an infinite wage.
"The amount that would make you happy" is a pragmatic minimum amount that would tempt you away from your current employment (or from further looking for other employment.) It's a buyer's price, not a seller's price.
> Why does their happiness amount affect your happiness? Would you be happier if they were paid less? Maybe they should be paid the amount that would make you happy instead of what would make them happy? Why? Their circumstances are different, they are different people, whose requirement for happiness is different than yours.
This is the problem with reifying the concept of an "amount that would make you happy." You've fallen into abstraction and spiritual condemnation. It's not illogical or irrational to not be happy with being paid less than you could be paid doing the same job, and it's insulting to treat employees like fools with this backwards logic.
If the employer is happy paying that other employee twice as much as you, why wouldn't they be happy paying you just as much? If they're happy with the deal with the other employee enough to continue it, why wouldn't they be happy with giving you that same deal? Really silly reasoning.