Besides the insane prices, one things I've noticed is that students don't get their student aid paid out until weeks into the semester, so you either have the choice to buy books at incredibly high prices at the college bookstore (higher even brand new compared to Amazon), or you have to wait 6 weeks before the aid is available for students to shop elsewhere.
Sneaky business.
The federal government is not okay with this, so they instituted a system of mandatory reporting where we have to keep track of whether or not a student shows up during the first few weeks. That way they know who not to send aid to when that time is up. If we fail to properly report this then the college is expected to send money to the federal government to make up the difference.
So it's not a trick on our part to get you to use the campus bookstore. I personally encourage my students not to use the bookstore, since I think marking up the prices on textbooks is inappropriate. I've also pushed hard for the adoption of open textbooks in my department, but it looks like that's going to be at least two years away.