When people cite that hundreds of billions could be saved in the war on drugs, where is that figure from?

A few years ago I saw a video of a swat team raiding a mans house. They killed his dogs (which were locked in their kennels) and then arrested him. He had 3 grams of marijuana on him. The operation cost close to $20,000 including the officers pay, equipment use, and planning. The man had to pay a $200 citation, and he sued them for killing his dogs and won an "undisclosed amount." This happens every day in America. State law enforcement agencies spend tens of millions a year doing such operations. The federal law enforcement agencies spend tens of millions every week doing operations against marijuana growers/users.