Given that most smokers/obese people tend to die right around retirement age, we probably aren't leaving much on the table (from a purely economic perspective). Smokers probably aren't missing enough days of work to cancel out the $60k they save the system by smoking (not to mention all the extra taxes they pay).

But there's more value to human beings than their economic value, hence my talk about non-monetary costs. There's very real suffering that happens, and I'm not sure that's something you can put down in a spreadsheet somewhere.