The headline is very shameless clickbait. Headline should read: Majority of used cars 3yrs old or younger are selling for >$20,000.
Economic reporting suffers from many of the same issues that scientific reporting does in that the headlines are a general idea of the research, blown out of proportion at best, and misleading at worst.
There's no sub 20k used cars under 3 years old because there aren't new cars under 30k. That's how math works.
looks at Cragslist
I see hundreds of cars in my area with a 4-digit price tag. I'm not sure where their info comes from, but used cars under $10,000 (hell, they say under $20,000) most certainly have not "almost vanished from the market."
It's for 3 years old and newer models.
Buy at five, sell at ten. Where did they get three years as a data point?
I can still regularly find used cars for $5000 or less. That still run. Perks of living in an area full of both gear and meth heads, I guess?