They know better than to buy sleevers, though.
Guns aren't an investment, anymore than a car is. Do some cars turn out to be worth more money than they cost? Sure. So do some guns. The trick is, which ones?
If you win on a gun, it is likely because you held on to it for a long time. The guy in the DGJ has been in the game for a long time, and bought his guns when they were much cheaper to get into, and, importantly, repair at the factory. I've got a hunch the rebarreled/rewooded guns (Langs?) he had photos of aren't worth as much as he seems to believe they are. No proof yet, since, they aren't for sale, but, time will tell. At his age, they shouldn't lose much more condition, anyway. If he keeps them too long, it won't matter if they went up or down, since, getting rid of them will be someone else's problem.
Like the investment brokers say, "Buy low, sell high". Like Sponge Bob says, "Good luck with that".
Best,
Ted