What reason is there for textbook costs?

130 bucks for a lousy softcover book on Macroeconomics?! That's what I paid today. Now this is my second time doing this, and I've fine tuned the strategy:

Buy the book, read/photocopy the first 1-2 weeks of reading for said class (all assignments on syllabus).

Buy copy of the book through some online, cheaper source.

Return book right away. The UNH book store gives until Monday to do any returns, less than a week.

But really, this book isn't beautiful. It's soft cover, 415 pages, with paper size the same as regular printer paper. Is there any reason for these books to be so expensive? The only one I can think of is that it feels good to fiscally **** students. I managed to buy a brand new copy for 80 dollars shipped on eBay at least; 50 more dollars invested.