The normal[1] physical Bitcoins have no physical value; they're just a paper wallet[2] with a certain balance, glued to a brass coin. The tamper-evident holograms are pretty cool.

[1] The silver/gold ones are so confusing that I won't address them.

[2] https://en.bitcoin.it/wiki/Paper_wallet

They're made out of gold/silver, and have an associated BTC value.