This is a really hard question to answer because I only ever bought a couple guns and "market rates" ever in a brief window in my career where I was finally paid pretty well. Everything else I basically stole, or got a deal on (even at the time).
At this point most of my collection in the category of; "Who knows what that's worth, it has to go to auction to find out". With kids I have been downsizing consistently, and the guns that stay are the unique things that can't be replaced.
If I had to guess, the biggest delta between what I paid, and what it would likely sell for today in a well advertised auction would be this thing:
If you peruse this for the factory documentation regarding all the modifications you will see why:
Update: 1920 Colt Factory Modified "Keith No. 5" for C.M. McCutcheon
Especially when you consider that this was the auction listing that I bought the gun based on:
**Colt Bisley Model Revolver | Cowan's Auction House: The Midwest's Most Trusted Auction House / Antiques / Fine Art / Art Appraisals
Yep, just the one picture, incorrect description, and a complete failure to note that it's what we know as a "Keith No. 5 ". They had misplaced the factory documentation, but Cowan's being a class act when they discovered it they went ahead and mailed it to me on their dime.
I paid a whole heck of a lot less than I thought I would have to, and had they sold the gun correctly there's zero chance I would own it. It's one of two guns I bought for what I consider "real money". The other one could absolutely be a contender for my "most appreciated". But, again. I would have no idea until I auctioned it:
This is Captain Bill Strong's:
hun slaying Springfield 1911:
That some jerk who owned it it after him scratched his name into:
I know what I paid for it, which was every penny I could scrape together for months, sold a bunch of guns, ate nothing but ramen. Ultimately it took every penny I had at the time, but I don't regret it at all.
How much has this appreciated, if at all?