However, compared to a lot of other sports that are complex and require a significant amount of equipment, climbing culture is a lot more weary of throwing money at the problem. Critically, a lot of serious climbers are willing to trade more money for more time climbing by selecting less-traditional careers or focusing less on corporate ladder-climbing.
I see it more that adult life is delayed, since there's the opportunity and privilege to delay it. It's kinda rich kids acting like their poor kids, 'cause that's kind of a cool thing to do.
Not everyone of course, but those $100,000 tricked out vans don't pay for themselves. Lots of career folk do roll those out on weekends, but some of those are owned by twenty-somethings. In the minority, you see some people scraping by.
Wut? Not expensive compared to what exactly? You know climbers are leaving material behind in mountains and trips themselves are expensive?
Why would "fit into backpack" be an argument for why something is cheap?
Most of this stuff (aside from the rope) will last for many years. Occasionally I'll lose a cam out climbing which is $50-80 to replace, but only happens a few times a season.
Compare this to skiing or mountain biking and you can see how climbing is a vastly cheaper sport.
Sometimes you have to sling a tree or rock in order to rappel. Sometimes gear gets stuck and you have to move on. Sometimes you drop gear by accident.
Regardless, any leisure time at all is a privilege. Working-class and poor people largely don't have time or money to do _anything_ at all, climbing or otherwise.
I also think you're putting a little too much value on 'adult life'. We can and should work on allowing more people from more diverse socio-economic backgrounds to enjoy more leisure time, not criticize the people that can.