You should get the expired editions on ebay for like $4
They usually only change 1 chapter and call it a new edition.
That's how they make money.
When I was in college, I saved a LOT of dollars that way.
It's legal too I think.
You spent $40 for an entire semester worth of books. Instead of $500.
Usually only 1 chapter missing, asked classmate to look in his book for that one chapter.