Collecting in itself is a very bizarre thing. Hardcore collectors "create" value and demand by analyzing the market of the items they collect, then choosing key items that are valuable and affordable they buy all of that model in order to artificially create demand (and a shortage) and then trade and sell those items off to build their collections. I have personally seen collectors do this with toy trains, rare books, ceramics, antique coffee grinders, etc... With guns, I would imagine, it is no different.
Personally, I really don't understand it. I just want a few old books to read, a few nice guns to shoot and a good glass of brandy every now and then.