I recently discovered cannabis prohibition costs about $4 out of every $100 moving through the US economy.

Additionally, marijuana is not physically addicting, while many Schedule III, and Schedule IV drugs are highly physically addicting and highly abused, such as Vicodin in Schedule III, and the benzodiazepines like Valium, Clonopin and Xanax in Schedule IV, which would be an argument for marijuana at Schedule V. 

The non-fatal consumption of 3000 mg/kg A THC by the dog and monkey would be comparable to a 154-pound human eating approximately 46 pounds (21 kilograms) of 1%-marihuana or 10 pounds of 5% hashish at one time. In addition, 92 mg/kg THC intravenously produced no fatalities in monkeys. These doses would be comparable to a 154-pound human smoking at one time almost three pounds (1.28 kg) of 1%-marihuana or 250,000 times the usual smoked dose and over a million times the minimal effective dose assuming 50% destruction of the THC by smoking.

800,000 in prison. Costs more than welfare. Funds extracted from education.