As an example, if you would pay $100 to extend your healthy life by one day (I know I would), that means each healthy day of your life you have ahead of you should be worth at least $100 to you. Assuming you have 10 years left of healthy life, your life ought to be worth at least 10×360×100=$360,000 to you. So a 1/1000 chance of death costs you 1/1000 * $360,000 = $360.