My take: The seller got top $ for the other cars, and the GN, being a "regular persons" car, was thrown in, as a incentive to "take it all".
Those other cars are a totally different "culture", and certainly aren't in the $30K range.
My bet is that GN was not in a "collector's stash".
They advertise it as a 3 owner. I doubt a serious collector would be into a used GN.
If they won't tell you who the collector is, I'd tell them to find someone else.
Lastly, check it well, for having a "factory authorized" repaint.