Details and citations in case anyone is curious...
"December 23, 2008 – NASA today announced its selection of the SpaceX Falcon 9 launch vehicle and Dragon spacecraft for the International Space Station (ISS) Cargo Resupply Services (CRS) contract award. The contract is for a guaranteed minimum of 20,000 kg to be carried to the International Space Station. The firm contracted value is $1.6 billion and NASA may elect to order additional missions for a cumulative total contract value of up to $3.1 billion."
"December 23, 2008 – NASA today announced its selection of the SpaceX Falcon 9 launch vehicle and Dragon spacecraft for the International Space Station (ISS) Cargo Resupply Services (CRS) contract award. The contract is for a guaranteed minimum of 20,000 kg to be carried to the International Space Station. The firm contracted value is $1.6 billion and NASA may elect to order additional missions for a cumulative total contract value of up to $3.1 billion."
http://www.spacex.com/press.php?page=20081223
and:
"The $1.6 billion contract represents a minimum of 12 flights..."
http://www.spacex.com/dragon.php