>Gold is valuable because it takes a lot of effort and investment to get any significant amount of it in high volume and purity. That's primary.
That's even more true for silver at present. For anyone who thinks silver is not highly undervalued, I challenge you to mine ore, refine, purify and produce a silver OZ coin for $15 US dollars. However, economic conditions under which the price would jump 10 fold or more for a correction would probably be so dire as to make other human essentials such as food, water, and firearms almost priceless.