It's not as though improv teachers are walking around buying luxury vehicles, though. The classes are as expensive as they need to be for the instructors to eat.
There's nothing stopping people from starting up a community improv troupe without formal training from a teacher, just as you don't need someone with an MFA in Performance to start a community theater group. There are enough books out there on the art form that a dedicated group could learn the necessary techniques on their own.
And high-level youth soccer can be way more expensive than even UCB-level improv classes.
I've looked at acting classes, and even beginning classes are much more expensive (2-5x) than any other type of classes I've taken, like martial arts, music, or dance -- even private lessons.
Do dancers not need to eat? Do musicians not study as long to become competent teachers? Why is acting priced so different from every other art?
Movie stars get paid orders of magnitude more than top martial artists/musicians/dancers, so more people try to be actors, so there's a larger market, meaning instructors can charge more.
Also depends where you're looking. The professional acting scenes in LA/NYC tend to choke out the hobbyist scenes (why see a community theater show in Manhattan when you can get sub-$50 tickets to a Broadway show from TDF?), so if you're looking for acting classes in those areas, they're directed at and priced for professionals.
There's nothing stopping people from starting up a community improv troupe without formal training from a teacher, just as you don't need someone with an MFA in Performance to start a community theater group. There are enough books out there on the art form that a dedicated group could learn the necessary techniques on their own.
And high-level youth soccer can be way more expensive than even UCB-level improv classes.