Health care costs for smokers at a given age are as much as
40 percent higher than those for nonsmokers, but in a
population in which no one smoked the costs would be 7
percent higher among men and 4 percent higher among
women than the costs in the current mixed population of
smokers and nonsmokers. If all smokers quit, health care
costs would be lower at first, but after 15 years they would
become higher than at present. In the long term, complete
smoking cessation would produce a net increase in health
care costs, but it could still be seen as economically
favorable under reasonable assumptions of discount rate
and evaluation period.
So, oddly enough, if smoking bans reduce smoking (evidence shows this isn't necessarily true) they only succeed in increasing the overall healthcare burden.
HatTip: Truth On the Market