My wife forwarded me the link below. Wouldn’t it be nice if Beckett, Tuff Stuff, Collector’s Digest used this same method? Maybe they do but I can’t imagine how. Some of the winning bids I find on eBay never come anywhere near “Book Value”.
Currently, they only track Vintage stuff but I’ll keep an eye on this site and post an update if I find significant additions are made to the site.