It is in lifetime medical care costs and there have been a few studies in Europe. The majority of medical costs is for age related care that grows exponentially with age, and smoking cuts decades off their life. Most smokers die before they get lung cancer, when they do it rarely results in surgery because they smoke, and it is easier to give a younger person chemo than and older person.
Also have you seen the kind of medication regimes that most 90 year olds take? Many of them take as many pills in a week as a 60 year old has took over the last decade or more.
You did not say lifetime medical costs initially but compared adding 2 years to a 90 year old vs 10 years to a sick 60 year old.
> Keeping a relatively healthy 90 year old alive for 2 more years costs significantly more than keeping an unhealthy 60 year old smoker alive 10 more years before they have a heart attack or stroke.