i go to a fairly prestigious private school, and you'd be surprised just how many of my friends driving benz and beamers have professors for parents, so you can't tell me they don't make any money. Second, some people just really like to teach. I have some incredibly smart teachers at my school, some of the best in the country in fact, who could easily land other jobs which pay way better, but rather choose to stay at my school and educate us. I realize in whatever school you went to, maybe they taught there because that was the only job they could get, but most of the teachers I know are incredibly bright, kind, helpful people I've ever met, who I have huge amounts of respect for.
ex. my calc teacher. He gave up being the principal of the school to just teacher, because he chooses to teach a full schedule (not one break... ever) and never complains because he's doing it for us. This man, I have endless respect for, and besides being brilliant, he's got everything he needs to become a professor or some other MUCH higher paying job, but he stays.
so "those who can, do. those who can't, teach" is the biggest load of bullshit.