Yes, people are NUTS about valuing their cars.
When I was Mustang shopping, I was looking at a low mileage '95 for sale in SC. I was considering buying a 1-way plan ticket to go down and drive it back to MI. This was back in 2004 when digital pictures weren't quite so easy to exchange and the resolution wasn't anything like it is today. All of the pictures looked good and I was debating the adventure, but at the time adding extra $$$ to an already pricey car had me on the fence.
In the meantime, a similar car popped up on Autotrader that was being sold locally. 1995 Cobra, white, with 25k miles - reasonably priced and no plane ticket needed. The pictures looked pretty good so I gave the number a ring. The guy told me that he was selling the car for his "Mom" who only drove it in good weather as a "weekend cruiser," "never raced," and that it was totally stock in excellent condition. The only change was that it had $1200 in new tires(?). The car was parked along a main road outside of an office building with a for sale sign in the window, so I could look at it that night, and he could swing by after his classes got out if I wanted to test drive it. I drove over and the car looked good... from a distance. When i walked up, the first thing I noticed was the tasteless cobra-head sculpted valve stem covers [okay, easy fix]. Then I noticed that the front bumper paint was all spidered, with some large chunks of paint missing down to the urethane, probably from hitting something [not ideal but not the end of the world]. The left rear quarter had a sizable dent in front of the tail light [okay, this is getting sketchy]. The interior was fairly dirty and the wear didn't seem to jive with the mileage on the cluster [very sketchy now]. I looked under the car and even though the floor boards looked clean, someone had tried to weld in subframe connectors [super sketchy, for Mom?]. It looked like they were attempting to stick weld them in, pushed the rod into the bead, and when the bead went cold and trapped the rod they just cut it off leaving 1" of it extending from the weld, then started another attempt right next to the last one. The result was something that resembled a metal porcupine with about 10 1" to 2" welding rod spikes sticking out of each bead [I'm out]. This thing was barely worth 1/3 of what he was asking.
After that experience, I decided that I was NOT going to fly down to SC and spend plane ticket money to risk finding something like this. I might consider it now given how far digital pictures have come, but the main point is that a good percentage of the cars people say are in "excellent condition" are not, and not worth anything close to what they're asking. And cars almost always look better in pictures than they do in person.