You are probably right when trying to sell the car in a persons local area, but if you advertised nationally, and said you would pay shipping (about $2K coast to coast), then I think you could come close to Hagerty's numbers. In the past year there have been a few posts on TT.Net that reflect prices close to these. Check out Bring Your Own Trailer.
Your target audience needs to be someone who WANTS a Z32, not just looking thru Auto-trader or Craig's List.