I believe its because the type of metal is a valuable one which makes it much more valuable than its face value which I dont have any issue against in which the same thing would go for if some one could have a raw gold 1btc. For me personally I dont see any prudency in buying such commodity as the case maybe where I would pay more than enough for the face value.
The metal is brass. The value is in the desire to own one of the first physical bitcoins ever made. If you aren't a collector, then there wouldn't be much value in that for you.