I agree with most of these responses, but would also encourage people to not put all of their eggs in one basket... If you are truly looking at buying/collecting guns as an investment, then you really should think about what % of your total dollars you are investing in guns vs. other options. I know the stock market is crazy right now, but remember, everything has cycles. As risky as the stock market may seem, there are also variables that can quickly/negatively impact the value of your guns (government laws/regulations, change in buying demographics, theft of your guns, etc...). How easily can you liquidate your gun investment if you have to; how about if regulations make it much more difficult to do so...?
I have struggled with this same dilemma, and have tried to be mindful of diversifying where I put my money. There are some financial/market instruments that carry much less risk, compared to other choices, much like some guns can be a bigger investment risk than others... I'd say if someone is buying 5k worth of guns per year, but has not opened a Roth IRA, then that person may want to talk to a legitimate financial advisor (not a broker, but a for-fee type advisor). Overall, if you are going to buy into the stock market, now is the time. It's also a decent time to buy guns, market is much softer than it was a couple of years ago.
Again, I would not put all of my money into guns, because if something changes relative to that market, you are SOL... I do know that, today, I will get a better return on my guns, than I would if I bought a new boat, sports car, golf clubs, power tools, etc... I like to think/hope that, down the road, I can at least get my money back on the guns that I have, but if worse comes to worse, I need a plan "B," so I'm not "all-in" on guns...