I very often ask myself that same question.

My classes are going very well, though. I remember my math professor was absent from his own class--he gave the students instructions to teach ourselves! And the scary thing is that we did teach ourselves (impressive for a group of 18 year-old immature freshmen).

I'm personally a very firm believer in learning outside of the classroom setting. But if you're having a lot of difficulty with incompetent professors, perhaps consider changing classes. Of course, switching to a different school is always an option. Hopefully, though, you can be in a position to feel satisfied with what you're paying for... you, as a "customer," should be reasonably satisfied with the competence of your professors.