I think perhaps you missed my premise. I'll give you emphysema (not contagious) but cancer and heart disease is just as drawn out and chronic (and expensive) for the non-smokers - after the hip and knee replacements, Lipitor, etc. A simple premise that I am working from is that, to my knowledge, no one has cured death or any of the nasty diseases that cause it. Smoking is politically charged and (like abortion), not a topic that is easily rationally debated. Let's more to a less politically charged topic.

Carrying extra weight (in some circles, the second leading preventable cause of death), if we tax the crap out of all foods/diets that cause obesity, do you think it will lower health care costs over a lifetime? There are way too many variables (with genetics being a major wildcard) to make any conclusive statements/correlations regarding actuarial certainty that costs will decrease.
To my knowledge, we don't have any truly longitudinal studies that show how many smokers who died were also overweight, heavy drinkers, highly stressed, etc. Until we can better isolate all of these variables, we may be barking up the wrong tree. To my knowledge, the only "proven" way to significantly increase lifespan (in female rodents) is a near starvation diet that slows cell division.
All in all tough to make a solid "economic" argument on fuzzy facts. Just my $.02