I agree a lot of the used scooters seem to be priced high by their owners. I've been watching them lately because I'm thinking about getting a Super 8 150 in the spring. The price of a brand new Super 8 150 is $2,299, and you'd be amazed at how many people with used ones think they are going to sell them for $2,000 or even more. Maybe they will find someone crazy enough to pay that, but if you think 5 or 8 years and a few thousand miles doesn't depreciate your bike more than a few hundred bucks, you're crazy. And yes, I realize a new bike is probably going to cost you more than MSRP once you pay dealer fees, but then again, I was able to get my 2018 UXV 450 for considerable LESS than MSRP simply because it was a leftover. The way I see it, I'd gladly pay up to $500 more for a brand new machine with a full two-year warranty than buy used.
I also think a big part of it is that people purposely put high prices on their machines with the expectation that buyers will want to negotiate. In my experience, money talks, and if you are looking for a used machine priced at $2,000, you have a pretty good chance of getting it for $1,500 if you show up with cash in hand.
My two cents...