I think it is very important to know what your collection is worth. Too often I hear, 'it's not about the money'. Yes, it is about the money. All of us only own the guns temporarily, and when we pass away, our collections will pass onto the next owner, which is usually an heir. We should have an idea of what our collections are worth, for the benefit of our heirs. Even if our direct heirs don't sell the collection, someday, someone will.
In my city, there was a gentleman who passed away about two years ago. This gentleman had a huge NFA collection. When he passed away, the family sold the collection for a 'good six figure amount', thinking that it was a lot of money. I saw part of the collection and tried to buy parts of it, but the holding dealer said that deal had already been closed. The 'good six figure amount' was grossly undervalued, from what I saw, and the buyer later bragged that he flipped the collection for a seven figure amount.
I am an NFA collector, and I have a sizable collection that is growing (that is guarded by a 24 hr surveillance camera and large bolted safe). I am sure to tell my family and spouse that if one day, if should ever pass away prematurely, that the generic looking AR guns in the safe, which if you google their used value comes back at $500, has a little one ounce piece of metal hidden in each of the guns that makes it worth $26,000 each.
I have nightmares about my heirs trying to figure out, 'what kind of gun this is', and then googling the image. That HK MP5K? It says here right on this airsoft website that it's worth $299! Bingo! *edit: for those who don't collect NFA guns, the MP5K with registered sear is going for around $32,000 as of this writing.
We take for granted our knowledge of guns. For those people who are not interested in the shooting sports, to them, a gun is just a mass of plastic/metal or plastic/wood/metal or wood/metal.