I've worked as an adjunct professor at a community college. Class sizes appeared to average around 20 students there, rarely above 30 and sometimes around 5. In that environment, $3500/class seemed pretty reasonable.
In any case, it doesn't matter if the class size is 10 or 50. You still need to prepare the same material, you still need to be there for the same amount of time. $3500/class sounds like a bargain to me. A TA earns more.
OK, but how are the professors expected to live on that ? Independently rich or retired cannot account for any size-able number. CC are subsidized by the state and county, or at least should be.