I'm not an expert, and I'm just spitballing here, but I'd say it's some combo of the following:
- cars last a lot longer, a 200k mile car still might have a couple years of solid life left
- inflation makes 2000$ now 4000$
- everyone is hard up for cash and needs to sell stuff at the most possible amount of money
- boomers are famous for considering everything they touch to increase in value
- a ton of used cars are off the market due to gov shenanigans
- the typical car is much pricier now, so the typical used car is also pricier
anyone got any others?