And that doesn’t include any additional savings on government expenditure on enforcement of prohibition, according to this Harvard study
Prohibition entails direct enforcement costs and prevents taxation of drug production and sale. This report examines the budgetary implications of legalizing drugs. The report estimates that legalizing drugs would save roughly $48.7 billion per year in government expenditure on enforcement of prohibition. $33.1 billion of this savings would accrue to state and local governments, while $15.6 billion would accrue to the federal government. Approximately $13.7 billion of the savings would results from legalization of marijuana, $22.3 billion from legalization of cocaine and heroin, and $12.8 from legalization of other drugs.
The report also estimates that drug legalization would yield tax revenue of $34.3 billion annually, assuming legal drugs are taxed at rates comparable to those on alcohol and tobacco. Approximately $6.4 billion of this revenue would result from legalization of marijuana, $23.9 billion from legalization of cocaine and heroin, and $4.0 billion from legalization of other drugs.
State-by-state breakdowns provide a rough indication of legalization’s impacts on state budgets, but these estimates are less reliable than those for the overall economy.
Cannabis can be beneficial for a number of medical treatments – “Evidence is accumulating that cannabinoids may be useful medicine for certain indications. Control of nausea and vomiting and the promotion of weight gain in chronic inanition are already licensed uses of oral THC (dronabinol capsules). Recent research indicates that cannabis may also be effective in the treatment of painful peripheral neuropathy and muscle spasticity from conditions such as multiple sclerosis. Other indications have been proposed, but adequate clinical trials have not been conducted. As these therapeutic potentials are confirmed, it will be useful if marijuana and its constituents can be prescribed, dispensed, and regulated in a manner similar to other medications that have psychotropic effects and some abuse potential. Given that we do not know precisely which cannabinoids or in which combinations achieve the best results, larger and more representative clinical trials of the plant product are warranted. Because cannabinoids are variably and sometimes incompletely absorbed from the gut, and bioavailability is reduced by extensive first pass metabolism, such trials should include delivery systems that include smoking, vaporization, and oral mucosal spray in order to achieve predictable blood levels and appropriate titration. Advances in understanding the medical indications and limitations of cannabis in its various forms should facilitate the regulatory and legislative processes.”
Igor Grant, J. Hampton Atkinson, Ben Gouaux and Barth Wilsey, “Medical Marijuana: Clearing Away The Smoke,” The Open Neurology Journal, 2012, 6:18-25. doi: 10.2174/1874205X01206010018. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3358713/pdf/TONEUJ-6-18.pdf