So what I am to understand is that the schools who pick very expensive books are not doing it because they have to do so. In fact, they are deliberately fleecing their students and their families because if some don't they are opting in.
Guess who will NOT be getting any donations anytime soon :/
No. Colleges do not pick class textbooks, the instructor does. *Sometimes* when an instructor insists on the very newest version of a very expensive textbook, there may be self-interest at work if the instructor wrote or edited part of it, but it depends a lot on the field. STEM fields require teaching the latest techniques, and you won't find those in old books, so unless some scientist has recently taken the time to write a free one, it's likely going to cost you.
Humanities and social sciences disciplines often still use paper books, or offer a choice of paper or ebook. Which makes sense, because
Wuthering Heights, or Upton Sinclair's
The Jungle is pretty much the same whether your copy is 20 years old or 20 days old.
However ... there is a movement in US higher ed (that has been spearheaded by librarians, actually) that is encouraging the use of open-source instructional materials in higher ed wherever possible. Sometimes that's a free virtual textbook written by the department or the instructor, and sometimes it's something created as a non-profit project by some scholarly group somewhere in the world. If your school doesn't encourage them, it should. (Schools, often through the Library's purchasing power, may also buy a multi-seat license to online textbook versions, and provide them at no extra charge to students as part of their tuition costs.)
If your student is in a discipline that requires new books to keep up with new technology & practices, and your college does not embrace the concept of open-source instructional materials, brace yourself for the concept of the dreaded
Access Code. The Code is actually a single-use limited-time seat license to access the supporting data and exercises that go with a commercially published textbook, whether you buy a paper copy or not. So, in many cases you can spend more buying a used book, because the code is only good for a finite period of time once activated. It usually comes with a new book at no extra charge, but constitutes an extra fee that must be paid if you purchased the book from someone other than the publisher. (DS attends a private high school, and we usually do not get books provided by the school. This year her high-school textbooks were $400, mostly used, but her social studies book, a new edition with a code, was almost $300 by itself.)