That hasn't really been true for decades, but it's especially wrong now. Used car prices have been driven to extremes recently thanks to a combination of demand from consumers wary of taking public transportation and a major shortage in the computer chips needed to make new cars. That superheated market is pushing prices higher, even for cars and trucks with six-digit mileage.

Historically, even when used car prices have risen overall, the prices on cars past the 100,000- mile mark haven't budged as much. But that's definitely not the case this year.

Last summer, the average used vehicle with between 100,000 and 110,000 miles on its odometer was worth about $12,700, according to Edmunds.com. That was just a few dollars more than it had been worth the year before. This year, that same sort of vehicle would be worth about $16,500, a roughly 30% increase in value.

These days, cars and SUVs can routinely survive for at least 200,000 miles. So a well-maintained vehicle with just over 100,000 miles should have plenty of usable life remaining. It may show some wear and, given its age, it won't have the latest tech and safety features, but it's still got plenty of time left to take someone around town.

Trucks are showing the biggest increases, something that's true among used vehicles of all ages and mileages. Average values for Chevrolet Silverado 1500 pickups with over 100,000 miles on them increased almost 50% to $27,000 while Ford F-150s of similar age are now worth roughly $26,000, a 43% increase. (These are retail used vehicle values — in other words, what a dealer could sell these trucks for. An owner selling the vehicle directly to another person or to a dealer should not expect to get quite that much.)

That sort of increase isn't confined to just these high-mileage vehicles. Trucks, cars and SUVs of all ages are going up in value, according to Edmunds.com's data. Partly this is because prices were just slightly depressed, or at least kept flat, a year ago during the depths of coronavirus lockdowns. Mostly, though, it has to do with increased demand for cars now. Average prices for used vehicles, overall, have risen about 27% since last year.

For cars and trucks that are farther past that 100,000-mile threshold, the increase in value is less but it's still remarkable. For example, vehicles with a little over 150,000 miles have gone up 25% in average value over the past year. Again, that's compared to very little increase in value normally.

Cars that have been driven 100,000 miles but less than 110,000 are, on average, 7.5 years old, according to Edmunds.com. That's still well below the average of all passenger vehicles on America's roads, according to research by IHS Markit. The average car, light truck or SUV being driven today is just over 12 years old, according to IHS Markit's most recent report. (Average vehicle age was pushed up slightly last year by a lack of new vehicle sales during the pandemic, according to the consulting firm.)

"It doesn't matter what age or mileage you have, your vehicle value is probably more than you ever thought," said Drury.