When looking the value of my `88 M5 on Kelley Blue Book (kbb.com), I saw that at the bottom of the page there was a link you can click if you paid/sold a car for an amount outside the range they quote. So I did, and they sent me an email asking what I acyually paid for my car. I paid a bove their highest value for it, so i filled it out and sent it back. I'm not sure if it helped at all, but if more people did this, then it just might impact the quoted values of these rare cars.