Other than BikePedia and Bicycle Blue Book, I know of no database. Some flippers are now using BBB, with some success, because the buyers may not be as educated as the sellers.

General rule, MSRP plus 1/3 the cost of upgrades, less 25-33% the first year. 33-50% the next two years, and then 50-67% thereafter, with a "bottoming out" in general of 1/3 the MSRP after 5 years. Then, the bike enters a value "dead zone" until, if or when it becomes collectible based simply on the qualities of the bike.

Unique bikes, as others have said here, with provenance or a pedigree, well, that's a very small and subjective market, and I cannot address same.

Good luck with whatever endeavor it may be. If it's for profit, keep your expectations neutral. If it's to keep bikes on the road, people riding, there is rarely much of a down side.

Welcome to C&V.