Just like bitcoin. It's all perceived value. Its a collectors item. A piece of bitcoin history. A 1933 Double eagle is now worth $7.6 million. You never know. Your grandkids will thank you.
http://mentalfloss.com/article/53557/10-most-expensive-coins-and-banknotes-worldI still have btc for which I paid $2.50. If there is something I want or like I'll pay a few BTC for it. Great value to the receiver but no skin off my back. Price is relative.