Sorry, it is. I've worked in higher education and I've seen it happen. What other explanation do you have for the sales of these ludicrous "textbooks"?
Some publishers may incentivize using their particular textbook, but there isn't some vast conspiracy to jack up prices. The fact is textbooks are a niche product with a steep demand curve that can be paid for with subsidized loans, of course they're going to be ridiculously overpriced.
And while calculus might have some public domain works that are acceptable, most fields have advanced pretty far since 1925, which might I remind you was before the discovery of DNA, penicillin, plate tectonics, molecular orbital theory, the neutron, the invention of digital electronics, Keynesian economics, Hemingway's first novel, etc.
> ridiculously overpriced
Well, you admit it yourself.
And the books aren't even any good!
300 kids taking a course in a 90 day semester, 10 copies in a library, each kid gets 3 days per semester with the class textbook. Would you pay 25000 for that semester of education? Maybe some students can go halvsies on a copy but the number of copies of the book that you need is roughly equivalent to the number of students. And before you say "well why doesn't the library just buy more copies" remember who pays for the library to buy those copies.
The professors don't make the changes to the textbooks, the publishers do. Professors don't like it either, they have to update all of their materials every year to keep up with the changes too.
No one is denying textbooks are expensive, I'm denying the conspiracy theory that professors and publishers are all colluding to manipulate the market.
It is really not that hard, these professors often write or collaborate on the textbooks themselves so they're writing them anyway. If the textbook is needed for learning and not just a way to get some extra money then this would be standard practice.
As a corollary, only very few professors actually have their own textbook and thus don't make any money whatsoever from choosing a specific textbook.
Finally, why would you deny someone money for work they did, typically in their spare time? Who else do you think should give away their work for free? Musicians? Doctors? Carpenters? Bakers? Do you accept money for the work you do?
Personally, I prefer decade old textbooks, hardcover, beautifully typeset, clear diagrams and equations, black and white. Of course that doesn't exist for every field. But try to imagine the complaints you get from students for teaching from 'obsolete' textbooks that aren't even in four color print.
