Understandable...especially regarding liquidity and exchange valuations. If we step beyond the idea of numismatics and look at Casascius from an asset diversification standpoint...having some amount of physical BTC would seem to hedge risk...for anyone wanting to invest (hodl) in Bitcoin really. Of course there are countless offline wallet solutions that serve a similar purpose, but Casascius has a well-earned spot at the top of the list in terms of potential appreciative value, in addition to its proven cold storage risk management attributes. A 1BTC silver Casascius actually holds ~2-3BTC of value in one coin, at the current market rates...there are not many other cold storage solutions that can claim that kind of premium value store. And as an aside, regardless of what one thinks of grading standards, having an early graded/dated and slabbed coin may provide some additional measure of security, if and when counterfeits become a major concern and enter the market en-masse...as is the case now with mainstream coin and card collecting.
With so few actual Casascius in existence overall, it would make sense that as more players enter the space, we may see increased demand for Casascius as a diversified BTC holding method...keep some liquid and some physical. This demand driver alone may move premiums back up, without even considering collectability.
Today's Ethereum news seems a fitting example of why people will always look for physical ways to hold value in an effort to hedge risk...
From ZeroHedge: "Finally, all of this just goes to show that when it comes to "money", whether digital, paper, or hard, there is simply no replacement to being able to hold it in one's hand..."
http://www.zerohedge.com/news/2016-06-17/bitcoins-largest-competitor-hacked-over-59-million-ethers-stolen-ongoing-attack