That's the point. Lung Cancer treatment is comparably cheap - surgery costs don't exceed some 1000's, the chemotherapeutika aren't too expensive as well. For Small Cell Lung Cancer, radiation is pretty cheap as well.
Then, after say two years, you're either dead, or recovered. No further medication needed. Arteriosclerosis and high blood pressure caused by smoking are more expensive; still, no match for those caused by obesity or diabetes.
You have to see it that way:
The typical heavy smoker with no other serious risks manages to reach retirement age while still being productive. Then, lung cancer usually strikes between age 60-70. A good portion of those affected doesn't survive. That saves 10+ years of annuity payments and medication for other diseases

.
Alcohol and obesity (especially the diabetes type 2 which almost exclusively is caused by it) affect many while they're still far away from retirement, while both also aren't causing a fast demise...
And, alcohol not only causes health costs, but "sabotages" production, leads to violance and accidents.
40 years of diabetes treatment, including insuline, other medication, polyneuropathia treatment, special diets, educational programs, sometimes surgery (to get rid of those rotten toes/feet/legs) are A LOT more expensive than treating lung cancer.
This does sound sarcastic, but it is true. The only question is if "Passive Smoking" also causes serious disease. If that turns out to be a major fact (I doubt it, though), the calculation may change.
Time to get my lunch break cigarette
.