Casascius usually sends them without Bitcoins, the Bitcoins are sent later.
So, no they aren't worth $10.000 when crossing the boarder.
(Also the Bitcoins are never on the coins in the first place, Bitcoins are always in the blockchain)
This bitcoin was minted in 2011 and it probably does have 25 btc.
But customs cannot stop it unless the coin is made of gold or they have certain legal document requiring declaration of bitcoins.
I guess Bitpay guy is just a victim of stupid mistake made by customs officer.