I was in the industry more than a decade ago, first as a writer, then as a publisher. A lot of this list would have been true then, too.
But there is one thing I wanted to respond to:
The problem is not that the books are overprice. They are overpriced usually for a reason. A BAD one.
That being the damn push for colour art and usually lots of it and the mania that this actually sells the book. Not the game. Kill this fad off and book prices would drop. But as long as publishers keep believing this lie then the books are going to cost alot more.
So, I had the opportunity to partner with a company that did two versions of their products, one with full color art, and one that was a plain text, well laid out version of the rules, but with no art. The page count on the latter was often up to 25% less. The quality of cover, paper, binding were the same - they came from the same printer. The cover of the black and white version was, if I recall, 2 color rather than 4 color.
Anyway, even though the artless version was significantly less expensive, the full color version sold tons better. I can only speak to convention sales, but our restocks for the full color version were about five times the restocks for the artless version.
And that 'fad' is why RPG books are full color - they sell better. A lot better. While
you may not want them, in general, RPG purchasers do.