Also don't forget to take into account the increased benefits to society. With a regulated and controlled legalization, more emphasis could and would be put towards harm reduction, which means that there would be a decrease in ER visits because people would be better educated.

Second, with more of an emphasis on education, treatment, and prevention, people who would otherwise spend a lot of their lives deep in the midsts of an addiction would be better able to overcome their addiction, and become a productive member of our society. Which means more money would be available to treat them.

Third, there would be new tax money from the sales of currently illicit drugs that could also be easily used to cover a lot of the medical bills you're talking about.