Thanks Blazed and Canary. Occurs to me that if BTC goes up a lot then the premium over the BTC value in a Cass coin is a loss. And if hyperbitcoinization happens then it's an epic loss. I heard the other day that even seed-stage investments in Coinbase didn't perform as well as just buying BTC. Makes it hard to use my fiat for anything else... I have to mentally separate my fiat into "for BTC" and "not for BTC" categories, and ironically buying a Cass coin would be in the "not for BTC" category.
Premiums seem tied to USD values and as Canary said when prices up Cas are down. Some coins have never had much of a premium regardless of prices (2013 brass, 25BTC, and 5BTC). Seems like only the silvers have kept the monster premiums.