Some new calculations suggest that the answer could be more than you think.
The Mortality Cost to Smokers
W. Kip Viscusi, Joni Hersch
This article estimates the mortality cost of smoking based on the first labor market estimates of the value of statistical life by smoking status. Using these values in conjunction with the increase in the mortality risk over the life cycle due to smoking, the value of statistical life by age and gender, and information on the number of packs smoked over the life cycle, produces an estimate of the private mortality cost of smoking of $222 per pack for men and $94 per pack for women in 2006 dollars, based on a 3 percent discount rate. At discount rates of 15 percent or more, the cost decreases to under $25 per pack.
Update: Econblogger Harry Clarke, who’s thought much more about smoking than me, posts his views. He also wonders whether we can reconcile the new Viscusi with the old Viscusi.