Hmm.. invest $50.
It sounds like a lot, but when you think about it, it's not that bad considering the textbook is great with its exercises and materials. And you'd probably only look into getting 2/3 textbooks at most (which is already hectic) and for the whole year.
I'm not one to talk about copyright considering how much I download (naturaly, because I am Asian) but for this, I just think it's fair and its always better to have a hard copy...