If you're not specifically talking about high-altitude climbing, then I'd argue this is wrong. There are famous *serious* climbers like Fred Beckey who managed to make climbing their entire lives on next to no income. Lots of serious climbers build up their rack from "booty" (taking material abandoned by other climbers in a range of situations, often bordering on questionably unethical), live in a van or a tent, hitchhike, etc.