The US Mint does not directly sell the investment-grade bullion Eagles. They only sell proofs and the burnished W mintmarked coins made for collectors. The Mint only sells the bullion coins to a small group of distributors/dealers. The reason for that is that they have to be capable of purchasing of multiple thousands of ounces of silver and gold Eagles. Check out this link
http://www.usmint.gov/consumer/inde...ericanEagles for more info on dealer qualifications. I buy them from my local coin dealer, he sells for about $2-3 over spot.