It depends on the instructor and the way the university is set up. I had classes as an undergrad which the professor had literally been teaching for decades - these guys hadn't spent time on a lesson plan since before the Beatles broke up. And they had grad students to grade papers and tests, plus teaching assistants the students were expected to see first before bothering the professor.

The test questions were just mixtures of questions from previous years.

So three hours of class, plus two (mandated) office hours. I'm assuming there was some time spent coordinating the grad students, but still... that doesn't seem like much work.