You could quite easily argue that smokers deliberately harm themselves out of negligence, and you could force them to pay for their own treatment, before or after said treatment. They make the choice and they shouldn't expect everyone else to bend over backwards to fix them, I agree.
But what annoys me about this is that no one ever brings this up. People who always advocate "banning smoking" or at least intervening to try and stop smoking always say "it's dangerous", and "X amount of people die every year from smoking" and "it's addictive" and so on. The ONLY valid argument I could see is the one about free healthcare, like you are all saying. And there are ways around that if people would bring it into the spotlight.
It's the only sensible reason I could understand all this fuss about, and no one ever talks about it.