Estimates of extraordinary health-care savings in research paper on medical marijuana laws and tobacco use

I just saw this notable research paper authored by Anna Choi, Dhaval Dave and Joseph Sabia under the title “Smoke Gets in Your Eyes: Medical Marijuana Laws and Tobacco Use.” The last line of the abstract merits placement in bold because it is such a bold finding:

The public health costs of tobacco consumption have been documented to be substantially larger than those of marijuana use.  This study is the first to investigate the impact of medical marijuana laws (MMLs) on tobacco cigarette consumption . First, using data from the National Survey of Drug Use and Health (NSDUH), we establish that MMLs induce a 2 to 3 percentage-point increase in adult marijuana consumption, likely for both recreational and medicinal purposes.  Then, using data from the NSDUH, the Behavioral Risk Factor Surveillance System (BRFSS), and the Current Population Survey Tobacco Use Supplements (CPS-TUS), we find that the enactment of MMLs leads to a 1 to 1.5 percentage-point reduction in adult cigarette smoking.  We also find that MMLs reduce the number of cigarettes consumed by smokers, suggesting effects on both the cessation and intensive margins of cigarette use.  Our estimated effect sizes imply substantial MML-induced tobacco-related healthcare cost savings, ranging from $4.6 to $6.9 billion per year.