First, I thought this was a coffee chain thread....
Could be a life choice. I almost died on mine.
As far as pricing them, you actually can bluebook them if you have a "name brand" scooter (e.g. Genuine, Vespa, Yamaha, Honda).
Are you looking at buying a Chinese scoot?
Below was my first scoot, that was Chinese and I sooped it up...took it from a top speed of 35 to roughly 45 (Lsoc bought it from me)

Then I got this beauty...but was forced to sell it as well.

