Price of an XF 1873 Carson City $5 gold piece in year 1974: $200 (Handbook of United States Coins with Premium List, 1974, R.S. Yeoman)That is 12.3% compound rate of return for 40 years.
High Plateau Drifter sale of an XF 1873 Carson City $5 gold piece: $21,000.00 in 2014.
A 105 bagger in 40 years!!
Over the same period, the S&P 500 did 11.2% compounded, assuming reinvestment of dividends (which would have actually been taxed). That ends up being a 68 bagger.
However, people are paying 10x the value of the gold content of these coins. It's a bad bet. They would make a great short, because the coins obviously do not generate any income, hence no negative carry.
Baby boomers are hoarders. Their formative experiences must have involved scarcity of material goods, which are now ubiquitous. See Paul Graham's essay on Stuff. Also, rising asset prices have conditioned them to hoard things that they think are investments - houses and cars - but are really consumables.