unions

At least theoretically in a labor market, wages are based on an equilibrium between demand for a given type of labor and the people who can do that labor. Their worth as a human being doesn't enter into it. The people who equate the wage equilibrium with worth as a person are indeed buttholes who are trying to use economics to justify their buttholeness, even though they haven't a clue what they're talking about.

Also, it doesn't necessarily speak to how difficult the job is for the individual who is doing it. I'll give myself as an example. I'm a quite good software developer and it comes easily to me. I don't have to work hard to do it, and it honestly has never been a struggle. But when I was younger, I had a couple of restaurant jobs. I had trouble keeping up. The difference? Software development hits a bunch of my areas of strong cognitive function. Food service hits a number of my worst weaknesses.

It's more about Qualifikation

exactly. people with such mindset deserve in fact lower pay