While it is uncomfortable to do so, of course we can. We do so everyday whether we choose to acknowledge it or not. Our govenment makes choices in deciding it will fund a cheaper treatment, over a somewhat more effective but considerably more expensive treatment. Is that not making a valuation on the worth of a life?
No doubt, people die while on waiting lists for treatment which could save their lives. Has the govenment not already made a value judgement by choosing not to more extensively fund this treatment?
Don't we all subjectively value a life when we choose to buy a new car rather than contribute to alleviate starvation in Africa?
Of course each valuation is subjective, and we tend to value our own lives and those of people close to us higher than strangers, or people in other countries, but our actions prove that we make valuation judgements on the worth of a life every day.
A smoker makes a voluntary choice to smoke despite knowing the risks to their health. They do so for their own reasons, not to abuse the health system, yet despite this, I don't really see why all of us should be forced to subsidize the cost of a choice which is made by the smoker alone.
I would have the same stance for participation in high-risk sports. If someone decides to engage in a high-risk activity, all the costs (including the healthcare) should be their's alone to bear. BTW, I do personally participate in sports and frequently injure myself. I'm fine to assume the costs of those injuries as I don't make reckless choices.
As I have proposed before, one fairer system is for users of the system to pay based upon risk (just as we do with auto, or life insurance). In this case, contributions by smokers, and others who engage in high-risk activites would help offset the costs that they incur.