My textbooks have usually ranged from $50 to $150 dollars checking Amazon, Chegg, and Half. I don't rent them because I usually sell the using Amazon as opposed to returning them to Amazon for credit. I tend to get between 50-75% of the cost back doing that.
I think I spent $140+ on one of my Stat books once that came with software,etc. After my freshman year, I started researching/asking around if textbooks were even needed for some of my classes and normally only needed to buy 50% of the books for my classes (my last semester of college I actually didn't even buy a single textbook).
For the ones I did buy I used Amazon or ebay, I think I used Chegg and another e-version rental place once. Nice thing was being a Finance major was a lot of books had "international versions" where I could buy a $100+ book for only $30-$40 brand new.