I've actually thought a lot about this and it's on my list of things to do. I'd write about the descent of illustration from how it was perceived in the Leyendecker era (like Rockwell was a freakin superstar) to how it is now where, because of social media and years of poor education, most people have this perception that not only are there a billion professional artists out there (which despite how it feels, there really isn't), that they are expendable and deserve to be underpaid. Just a big depressing book about fundamental rules of commerce failing to work: where despite there being so much demand and despite the quality being better than ever, the price of commercial art remains so, so incredibly poor and only seems to get worse.