"Imagined" hey. So smokers dying of diseases doesn't cost the NHS any more money? What planet are you on dude? Or are you saying that the cigarette taxes cover this?
In 1999 taxes made up over 80% of the price of cigarettes in the UK. For some reason I don't think the percentage has dropped much since then. The average smoker consumes maybe a pack a day. Say, for simplicity's sake(I don't really know what they cost in the UK) that a pack of cigs costs 3 GBP where 2.4 of those are taxes. Now, say the smoker has been smoking since age 20 and croaks from smoke-related illness when he's 65; that's 2.4*16425 days = 39420 GBP in tobacco tax alone. That and the fact that he never reached retirement age probably makes him far less of an expense for society than his non-smoking fellow man, medical expenses or no.