The link I posted under the air Force coin is a link to where you could buy the coin. They're the only sore that sells it and only 1000 of those coins were made. That coin is a low mint # and I have the first Certificate of Authentication issued with these coins.
The bar holds a true face value to it but it's much lower than the silver values of it. Only 350k of those were made making it a little more rare and they're not made every year. For instance there were 17 million silver American eagles sold last year.
The company that mints the coin, the amount minted, the quality of the image on the coin, if there are any errors on the coin all effect cost. Most of what I've sold here is just basic generic stuff and I normally sell it below online pricing. Most every coin sells for more than spot.