A one-in-a-million chance of dying.
For sudden, one-off risks. A skydive is about 8. Driving 370 km is about 1.
Thirty minutes of life expectancy.
For slow, daily habits. Two cigarettes cost one. Twenty minutes of exercise earns two.
Chance of dying × the years you'd lose.
So a risk costs you time, on average. A skydive at 45 costs about 2.5 hours of life. The older you are, the cheaper the same thrill.
Known risks, measured. Approximate averages, mostly from David Spiegelhalter's work and national statistics. Your mileage will vary, literally.