Classes start tomorrow, and I bought books today to take advantage of a 10% discount at the campus book store. Purchasing the mandatory books cost $420, and I haven't bought any of the recommended supplementary books yet. Fortunately, my scholarship includes a book voucher for $500 per semester, but since the voucher is only good at the university-owned store, I can't shop around for the best prices.
Why should a single paperback text cost $140? I have serious problems with textbook publishers. Our understanding of some subjects, such as cell biology, is changing rapidly, and frequently releasing updated editions makes sense. A book on classical electrodynamics, on the other hand, should be good for many years. An introductory calculus book should be good for decades, if not centuries, once they find and correct the inevitable errors. By releasing new editions, they make used books worth very little and force students to shell out for a brand new book that may not have many changes.
I respect the importance of choosing a book with good pedagogy, but surely there are some cheaper books out there that would do the job. Is there a reason math professors never consider the textbooks available from Dover? Why do they force us to buy books with pricey bundled cd-roms we don't use? I've had one professor who told us we could search the old edition of our textbook on PubMed and thus really didn't need to buy a book at all, but most aren't so sympathetic.
At this point, shopping around helps a bit, especially if you stumble across an international edition. Try Barnes and Noble, Amazon, and ABE Books to see if they can beat the prices on campus. Also, try buying directly from former students; since the buyback prices offered by the bookstores at the end of the semester are often a joke, there might be plenty of students eager to sell. I'm lending my brother my old Diff. Eq. book and student solutions manual to save him the cost of buying his own. If your college library keeps books on reserve and you can get them when you need to study, that can be a good way to reduce your costs, but it isn't always an option. Sharing a book with a friend, especially a roommate, can be handy if you can work out a schedule so you aren't fighting over it the weekend before a major exam. Project Gutenberg can sometimes give you access to books you need to read for literature classes. I wouldn't recommend forgoing a required text in an attempt to save money even though I know people who've done so. Doing the required reading makes lectures much more comprehensible and keeps you actively engaged in the course.