Gently used at 100k seems like a strong ask. I commute two hours a day and get around ~20k miles a year. The car would be five years old at the point of 100k. Quicker than that and the person that owned it drove the crap out of it. Plastic and trim is squeaking, stains, scratches, etc. I dont personally care about any of that but I expect it to be reflected heavily in the price.
Then you look at the asking prices for larger SUVs with 200k+ miles and its even crazier.
My first car was 10 years old when I got it, model year 1986. I did maintenance myself with the help of my father - oil, brakes, rotors, that kind of thing. It was 5 more years before it needed real work (bad alternator, bad fuel pump) and another 3ish years before major failure. A couple grand kept it on the road. After I sold it I still saw it around town for a number of years.
My point is, cars last far, far longer than we generally assume if you take reasonable care of them!
Those SUVs were expensive new as well. If you head over to the new car lot, it's not hard to spend $60k on an SUV, even a domestic one with a Chevy|Ford|Jeep badge.
These are the kinds of vehicles that everyone wants to drive (along with trucks) and 72/84 month loans have been common for a while now (even for lightly used cars). So that sets price floor for trade-ins, since people can only roll over so much negative equity. Then you have to factor in that car sales in 2009-2012 were 50-60% of what they were in 2019.
So, demand is high, and supply is low. It makes sense that used SUVs are expensive. Once you start looking at less desirable models, like coupes and sedans, then prices drop considerably.
It's possible if you're like my friend whose job was to drive all around Europe hauling specialised parts for construction equipment, sometimes doing 2k km in a single day.
I think he did 60k km (37.5k miles) during the first year, but you couldn't tell that from the shape the car was in, since he cared for both the exterior and interior.
The only thing that showed any visible signs of aging were the windshield wipers - he had so much on his plate that he couldn't squeeze out a few minutes to refresh them.
Then you look at the asking prices for larger SUVs with 200k+ miles and its even crazier.