First off they are not becomming more and more uncommon. They are becomming more common with more and more companies releasing convertable models for 2012 than 2011 and more available in 2011 than 2010.
I feel the price is high being the loan value has a lot to do with car values.
I am seeing more and more SRT's selling in that price range and if purchased from a dealer some of those are available with the warrantees.
Leave it listed at that price but be ready to accept a sensible offer.

Good luck with the grand child. Maybe you could use the car to teach her the impotance of caring for classic automobiles
Mike