When I was doing Algorithms and Data Structures at the University of Otago, the required textbook was Cormen's Introduction to Algorithms first edition. More than $NZ130 at the time, and we got a few weeks into the course before they told us we didn't actually need it for coursework, they just wanted to make sure we had a copy.
I see it's available for $US6.61 used on Amazon now...
When you say "they just wanted to make sure we had a copy" you mean - they made you buy it as a "requirement" (that there was no way around it), or they just told you and most of you bought?
And by "they" you meant the faculty (professors etc) or college administration or some other office office? Just curious about it. I am from India and there are no fixed text books here (at least the colleges I know about - central Govt. funded). There are syllabi and you are free to study the course with anything you want - books, or no books. My college library solved textbook problem for almost 40% students and rest were solved by hands-me-downs from seniors, 2nd hand book stores (some of them have very capable xerox machines too), and then there's "online".
I see it's available for $US6.61 used on Amazon now...
edit: had the price about $50 too high.