Protip from a guy with two university degrees obtained over 7 years:
The only textbooks you should ever buy are those that meet ALL the following criteria:
1. Are listed as 'required' on the course syllabus;
2. The professor confirms to you, in person, contain exercises that are mandatory course work for the class and which cannot be obtained elsewhere;
3. Cannot be obtained from a student in the previous semester or year class
4. Do not have copies maintained in the facility library/ies
5. Are significantly different from previous editions in the book in content, and not just page numbering
6. You cannot buy one copy and share between a few friends.
By the third year of my first degree, I managed to buy only 1-2 books per semester. One semester I bought no textbooks. My second degree was filled with a lot of sociology/psychology/history, and had quite a bit of required reading necessitating my own books, but they tended to be $20-$30 per book, not the several hundred that some of my genetics and biochemistry books cost (and could not be resold due to edition changes).
My first year of university, I spent over $1300 on textbooks. My last, I spent $140.
University- and college-level textbooks are an extortionate scheme by publishing companies (and the professors that write the books). Often, the sole difference between one edition and the next is nothing more than page numbering. I cannot emphasize enough how little you should or need to support this horrible exercise in monopolistic capitalism.