>>740110Currency is a token of a social relationship, not something inherently valuable in and of itself.
Why does the deed to a house worth ~a house? Why is a legal contract for 100 tons of copper worth ~100 tons of copper? They too are "just paper", or perhaps even just records in a digital database. Their value only makes sense when you realize it flows from the relationships between human beings (the state will enforce your ownership of the house and punish deviation from the copper contract), not from any inherent property of the paper itself.
Copper disks can even wind up having the opposite problem, where the copper in a 1c coin is worth more than 1c.