I think/hope we're talking about different things. I think you're saying that employers pay employees as little as they can, not according to some formula base

I think/hope we're talking about different things. I think you're saying that employers pay employees as little as they can, not according to some formula based on the value each employee generates. Aside from some very specific exceptions, I think that's very true. But then we need to explain why all companies don't just pay minimum wage! I claim that prices (wages) on a labor market, like on most markets, is determined by supply and demand. Obviously, companies that pay employees more than the value they generate will run out of money and die. This sets an upper limit on wages. The lower limit comes from companies outbidding (demand) each other for workers (supply) as long as it's profitable. In aggregate this means wages will converge on on some large percentage of the value generated by the typical employee.