The people doing the hiring may have enough information to produce an efficient market for a given job role, but I don't think the mechanism for the selection of job roles looks much like a supply-and-demand market.
Consider system administration. As a simplified example, you could have one equilibrium in which you have one low-skill employee for each 50 computers, or a different equilibrium where you have one high-skill employee for each 500 computers.
If the industry as a whole settled on the first, a particular company would find it hard to switch to the second: it would be hard to even gather information about how well it would work, because the operating systems available would be designed for the lower levels of automation that the first model implies.
In cases where two equilibria are viable, I think where we end up can depend on whether the employers feel that a given sort of job "ought" to be a high-paid professional one or not.
They teach ~100 students every day, so tens of millions in future earnings depend on them.
Does their pay reflect this? All the good teachers I've met, could be making more elsewhere.
Anyone who consumes a good or service is aware of its market price, and is very well capable of comparing it to any value offered. There is no need to pull a classist conspiracy card because, in the very least, those responsible for doing the hiring have interviewed multiple candidates and heard what wages they were asking, and were more than able to compare offers.