This isn't the case for diabetics, but people with high blood pressure and high cholesterol can inexpensively take medications to treat their conditions without changing their diet and taking up exercising. Of course, this isn't the case for all such medications, say if the prescribing doctor has expensive tastes or if the patient has not met adequate results from the relatively inexpensive alternatives, and dosages will need to be increased overtime, but for the most part people with these conditions can delay serious health events, such as heart attacks or what have you, while continuing to lead unhealthy lifestyle, ultimately making the serious health event inevitable. That's not to say that this is the case for all patients on these medications - such health problems are often genetic - but it does bring up an interesting question over medical treatment.
For example, if one suffering from these medical conditions does follow in the aforementioned manner, unquestionably they will be placed on more and more medications, thus costing more and more money, but it really just turns into a rather expensive manner of delaying a serious health event, which is significantly more expensive and, if the event doesn't prove deadly, will result the prescribing of more, and probably expensive brand names, medication. Given the prevalence of these occurrences in the United States, it's not really surprising that health care costs are so expensive.
That said, I can't really say that I'm healthy either. Though my diet isn't that bad, I drink more than I probably should and I don't exercise whatsoever nor do I have an interest in doing so. Genetically, I'm lucky, but we'll see if that lasts as the decades go by. Perhaps being confronted with tacking on a few pounds would convince me to change, since I've never close to exceeding 10% body fat. On the bright side, I believe that food choice in the country has improved a lot and certainly people are becoming more aware of these problems, and though some disagree, I think awareness can make a big difference -- if not for the current adult generation, then for the next.