[ghaff]

>It's supply vs. demand, that's all there is to it.

Yup. There may be good demand because of force multiplier or return to capital or whatever. (Which are just ways of saying that the work translates into something people are willing to pay for.) And there may be (somewhat) limited supply because it's not something everyone wants to or can do, whether through formal education or otherwise.

But, take either supply or demand away and the salaries commanded adjust accordingly.

That I could spend 10 years becoming an expert on medieval German literature doesn't necessarily mean that I could command a high salary however rare that expertise.