I understand this is fail safe, but I don't totally agree with it. Investments buying guns and other commodities CAN pay huge dividends if one isn't paying credit card interest on said purchases and can hold them for 10 years or so (at least 5) in new condition. You can see how much more inflated gun and optic prices are now verses 10 years ago. The longer you hold it, the more you make - exactly like stock investments except there's less risk. Unless your collection gets stolen, burned up, or laws pass prohibiting you ever transferring your firearm, they are very safe investments. Think about it this way: you are spending your money when you contribute to your 401k. You are purchasing stock (spending money) or mutual funds of some sort in hopes of it growing and making a good return. Real estate is maybe the best investment except for the taxes you have to pay on it. The population is going to get larger and the amount of room for each of us is constantly decreasing, therefore becoming more valuable. Prices may fluctuate in smaller areas or depreciate due to any change in surroundings making it less desirable.
This is true only if you don't "short sell". If you offer it for sale in under 5 years or in less than perfect condition, you're going to generally have to eat part of your original investment and your statement is then 100% true.
I typically fall into the latter category where I feel the need to move things out that aren't going to get used rather quickly after the purchase of something else. I also build lots of rifles for a hobby. Some of the work I farm out around the country to those who have the equipment and skill to produce what I want, while I do some of the work myself at home. Sometimes, I have an idea that I may use the new purchase for a custom build if it doesn't work out as intended at purchase. Sometimes, though, I may snatch something up with this intention and then think about it and really scrutinize it later, and wonder what I was thinking. I.e. I have this beautiful Savage Model 12 in .204 Ruger that has a BEAUTIFUL finish and someone professionally painted the synthetic stock with a textured paint that stays in there very well. It appears basically unfired. Got an ok deal on it, but I was thinking of building something with it - didn't have any interest in a .204 Ruger. I had just had a barrel made and bought a donor rifle for a .25-45 Sharps build. Not much else I could do with this since I'm only interested in calibers larger than .224. A .350 Legend?? Nah. Don't need it. Have too many other things that would fill that niche already. And honestly, it's so unique with such a beautiful blued finish in high condition that I am not sure I'm OK with tearing it apart. It has a bull 26" barrel, so it's top heavy, and heavy in general, it isn't a predator rifle you'd pack for long hikes. So nothing to do but sell it as is, most likely. But without seeing it, the likelihood of someone being stirred to purchase it for what I paid isn't Grand. And that model likely won't be worth significantly more in 10 years.
So if I'd followed your rule, would I have more money in my pocket today? Absolutely. Because I don't practice what I'm preaching here too often, I'm losing SOME money... BUT... I can say for sure that at least I have something to show for my money that can be liquidated in emergency for the majority of what I paid. IF I had not purchases shooting-relates items and hardware, I would have spent the money somewhere else and probably not had anything to show for it. The bottom line is savers are gonna save and spenders are gonna spend. I am trying to spend more frugally, however.