[m463]

I would also say, people make more money doing stuff that's hard. (and of course the bar goes up)

[ghaff]

I'd say "hard" is a necessary but not sufficient condition. People (individually or in the aggregate) also need to be willing to pay you specifically a lot of money for what you specifically bring to the table that, in many creative fields, requires being very top tier (and lucky).

In the arts, the equivalent of a mid-tier developer makes jack squat.