It is supply and demand.

Car makers made a fundamental mistake at the beginning of the Coronavirus crisis which was thinking that any kind of crisis would lead to people not having money to buy stuff and thus a drop in demand for cars.

Turned out that economic stimulus would flow like water and also the virus would be very good for demand for cars because it gives people a reason to move further away from crowds and also a reason not to take public transit.

Carmakers cut back their orders for chips and then realized afterwards it was a mistake, by that point the chip shortage was well under way.

Thus the supply chain for new cars is disrupted as is the supply chain for getting parts to fix existing cars.

Since many consumers have a choice of fixing an old car, buying a new car or buying a used car the price of used cars is up.

My projection is that the chip situation turns from boom to bust around 2025 or so.

Chip shortage due to COVID screwing with international logistics. Most modern cars are computerized, so no chips means new cars can't get built.

No new cars == prices are up for new cars, and since people can't afford new cars they hammer the used car market. Which drives up the cost there, too.

This was asked already like 2 Weeks ago