I teach computer programming at a vocational school. I have to follow the State's frameworks as to what my students are supposed to learn, but it's up to me which books I use. To cover everything I'm suppose to, my students have to buy five books. The most expensive ones come from Cengage, which is a scholastic publisher. Most of their stuff is top-notch. Each chapter in the book has questions and exercises for the students and the teacher's book comes with PowerPoints, test banks, etc. One book costs my students $145.
I also use Murach's books, which can be purchased from Amazon for around $35. But there's no questions or exercises for each chapter. I have to come up with my own stuff.
Used computer books is pointless. Most programming technologies get updated every year or two and the students like to keep the books for reference anyway.