There has been a common idea that copying a book is better than buying the original book. I did that in the past while i was a student, but there was a reason behind it. The college didn't negotiate with the publisher to provide a textbook for the students to buy, so the students ended with an original book which was so expensive at that time (i was studying in bachelor degree when IDR's rate was in a bad shape related to USD).
Things have changed now. We are trying to make our process of learning new knowledge become better by trying to provide a low cost text books to the students. The distributors will give a very special discount if it used by the students and based on what i seen, the difference is so high. You will not get those price at normal price such as in Amazon.
The problem now lies to the students, whether they would use this chance to buy the book or not. It's not just about the price and the information in the book. It's about the add on materials that are only included if you buy the original book since some books has an additional companion websites which gives you access to additional materials not available on the book itself. I think if the college has given you this opportunity, you should take it very well, because not every college is willing to deal with the distributor to handle the process.