My oldest has taken several AP classes. All the ones that were offered for his particular grade level. He LOVES them and he isn't your typical book worm.
We also aren't required to pay for the test, but all the kids in the class take it. I am learning more and more how much I love my school district. I would hate to have to pay for those exams.
I had no issues paying for any of DD's AP exams - she earned a total of 20 credits for 4 AP classes she took in high school. We also paid $85 for a college registration fee (and $5 or $10 for a transcript) for a dual-enrollment English class which was another 3 credits. I don't know many colleges were 23 credits would cost approximately $400. Heck- one credit at DD's school cost almost $800 - EACH.

She did very well, and went on to grad school, and has since graduated from there.