I think the study is presenting a point that's independent of the unhealthy lifestyles. An unhealthy lifestyle probably determines how much healthcare is needed, but the article is discussing the cost *per unit *of healthcare.
If the market wasn't rife with "criminal enterprises", you might even expect having an unhealthy population to lead to prices drops through economies of scale.
Our drug companies are criminal enterprises, and our population is insanely unhealthy. Fix the unhealthy lifestyles of the people, and you take away the leverage of those criminals.