S.P. Fjestad's Blue Book is the generally-recognized industry standard for pricing used and collectible guns. Bear in mind that it's just a guideline, a rule of thumb. There are going to be regional variations (although those have flattened out somewhat in the days of the internet,) prices at auction will almost always be higher, and I've always maintained that they lost connection with reality in postwar S&W pricing about ten years ago, although they've gotten a little better in the recent past (srsly, $450 for an unfired, in-the-box, P&R Model 28? I'll take every one you can find at that price.)
I rarely bought my own Blue Books since, you know, I had one I could consult at work. As a result, I only have a couple at home currently; the 23rd and 29th editions, corresponding to 2002 and 2008. After typing that bit on Colt pricing yesterday, I decided to take a look at what the book had to say.
For starters, we'll ignore pricing in the "100%" grade, as it's largely mythical, especially in antique guns. 100% (referring to the amount of original finish left on the gun) is generally held to be the Platonic ideal, and even the prettiest guns fall short unless they are truly exceptional. In my years of walking the aisles at gun shows and standing behind counters, I can remember most of my "100%!" moments fairly clearly.
Still, even working with the 98% and 95% pricing grades, antique Colt autos exploded between 2002 and 2008. In '02, a GI Colt 1911A1 booked at $625 in 95% and $895 in 98%; six years later the same gun in the same condition showed a book value of $2,700 to $3,200. That's crazy. That's Dutch Tulip Bulb, California real-estate, U.S. Treasury Department crazy. Bear in mind that these prices are for original, unrefinished guns in primo shape, the kind that tend to change hands at auction or between collectors, but it affects lower-grade guns, too: The 60% beater (and a 60% gun is homely!) that rated $325 in 2002 would fetch as much as a grand in '08.
Anybody who attends gun shows has seen it. Re-arsenaled GI "mixmasters" (guns with parts from Colt, Remington Rand, whoever) are priced at $800 and more. This has spread to lesser Colts, too. For example, in '02 a really nice 98% Colt 1908 Vest Pocket booked out at $425; the same gun in '08? $700. The early Colt Pocket Hammerless that rated $720 in the 23rd Edition rated $1,600 in the 29th.
Do you know what soaring prices on collectibles are usually a sign of? Inflation. I'm afraid to pick up a copy of the 31st Edition...