Over time I have seen some publications that ask themselves the question why artists generally have low incomes, including 'Why Are Artists Poor?', the PhD-thesis of Hans Abbing, who's probably the most famous Dutch theorist on the economics of art. That 300 page document has a reasonable understanding of economics, but almost zero understanding of contemporary art and thus unsuprisingly doesn't come to any satisfying conclusion.
Yet it shouldn't be a big mystery why artists are poor and knowledge of art or the art market isn't necessary to understand it either.
An artist's practise is an R&D heavy, thus capital intensive, business, that commonly produces a limited output to a market that is limited by definition because the goods it produces will always defy the common appearances of whatever other goods are sold at that time. *
That by itself should be enough reason why most artists aren't turning huge profits and then we haven't even talked about the lack of reliable information on goods or the vast supply surplus or any of the other ways the market fails.
But please continue to wonder why artists are poor and I will continue to wonder why people with negliable knowledge of the field they work in can obtain professorships.
* Even in his thesis Abbing notes that painters and sculptors pre-19th
century had generally decent incomes.
That's because those businesses produced a single style, had an output that was similar to the craftsmanship still present in many other markets and its products where relatively clearly defined, so that a functional market of informed buyers could arise.
The explanation he gives for the change, a strong need for authenticity in art since the 1850's, however is such a dull and ill-informed cliche that I don't even know what to say about it.