[spit2wind]

I taught a remedial math class. There are thousands of books for such a topic. I was required by the university to use a specific new edition (something like 9th) from a specific publisher. I went to the university library and found the 2nd edition. The questions were more or less verbatim but in a different order. The lesson portions were more or less the same and tended to be better. I explicitly directed students to this edition, which they could purchase for something like 2$ (vs $150). In 10 years in post-highschool eduction, and 4 institutions, I never once heard or had a teacher do that. It's a choice and the majority of educators don't do it.

Tip for learners: find an early edition of a book. They're often vastly cheaper and much better written. It stands that if a book warrants a 12th edition, then the 1st edition must have been decent enough to get wide adoption. Often revisions are bloat or, when they're not, it's educational to see the difference between then and now (eg Andre Tanenbaum's OS books)