I can understand that, but I think the two markets are different enough to be worth pointing out. People who buy used cars are often buying something a few years old. By the time a car is ten years old, it's being traded around for a tiny fraction of its original cost, and maybe even headed off to be junked/recycled. Maintenance costs are starting to skyrocket, and because of all that, people tend to trade up frequently.

A used airplane is probably decades old. It's probably selling for a similar price to what it originally went for when it was new. Maintenance costs are high, but they were high when the thing was new, so that's not particularly remarkable.

I'd wager that the majority of light aircraft flying in the US today would qualify for "antique" license plates if they were cars. It's a substantially different market, where the equipment lasts longer and buying used is much more common.