Matt Cutts, the unofficial Google blogger, wrote on his blog the other day some helpful advice for us college students:
A few days ago I was in a college bookstore that wanted to charge $178.60 for a copy of Mathematical Physics, by Eugene Butkov. $178.60? For a used, paperback book? Grrr. I took a picture of the UPC code and/or ISBN number.
You can search for an ISBN or UPC code (e.g.  ) on Google or other search engines and usually find out a product pretty quickly. I found a copy for $115.34 at Amazon, plus eBay had a hardcover copy with a current bid of $23.20. For a college student, $60 to $150 is a lot of savings.