I think alot of it, is back in the day, you used to have to "want" to sell something to get it listed (in the newspaper or Advertiser type rags). You had to make a phone call, pay some money and you couldn't change it or pull it once you listed it. And if you didn't sell it, you had to pay again to list it. (I'm 49 years old but typing that made me feel like 70, lol)
Now, you can not only list something nationwide without ever getting off your couch, you can also search nationwide, and for cars/trucks/motorized toys, you can see how much every overpriced dealer from here to Kentucky is asking. Oh, and you can edit the ad at will for free or next to free.
Now the weird people can eff with their adds constantly, forget or refuse to put a phone number in and then not check emails, change the price if they get too many calls, i think some just constantly put up adds for every piece of crap laying around their crappy ass house, in hopes of selling "something".
And yes the number of good project vehicles, classic cars, has gone down and the prices up.
Basically the internet ruined private party sales....covid has made it worse and supply chain issues have jacked the prices, indirectly, even more!
A good economic correction will take care of the prices, when tat happens, but I doubt sellers (and buyers) will become less flaky.