Here are two good examples. I’ve gone back and looked at the history of these and even found the photos and in some cases videos of what they looked like at each sale, plus I’ve seen the current versions in person.
My sense is that sellers want the maximum gain for upgrades they didn’t do! That seems crazy. OTOH, if prices have gone up and that’s the market, then they’ve gone up. I’m just trying to figure out how much.