According to the US Office of National Drug Control Policy, in 2010 The U.S. federal government spent over $15 billion dollars on the War on Drugs.

(That is a cost of about $500 per second, but that’s just the federal government, state and local governments spent at least another 25 billion dollars.

America is still the single largest marketplace for illegal drugs. One estimate is that around thirteen million Americans still occasionally buy illegal drugs, whist an estimated 5 and 6 million have more serious drug habits. The government estimates that users spend approximately $60 billion dollars a year.)

You can follow an up-to-date calculator online.