Space agencies track the risk from things like asteroids, but it's unclear how much to spend on this sort of thing. The Planetary Society writes:
Near-Earth object surveys have found (we think) 98% of the largest objects that present the most risk, reducing the actuarial risk due to asteroid impacts from 250 fatalities per year to 64 per year. Based on past discovery rates and projecting forward through proposed future projects, over the next 16 years, we should achieve 90% completion of discovery of asteroids larger than 140 meters in diameter. The effect of this 16 years of work -- at a cost of roughly a billion dollars -- will be to reduce the actuarial risk to 33 fatalities per year. If you see asteroid surveys as a form of insurance, then you're spending about two million dollars per fatality avoided.Is $2 million per life a good price? It's repellent to even think about putting dollar values on lives, but we do it all the time. If you buy the cheaper car instead of the safer, more expensive one, for example, you're trading off money and safety.
US government agencies define the “value of a statistical life” somewhere around $7 million. If they're deciding whether to institute new safety regulations on seat belts or air pollution, for example, they want to know whether spending billions of dollars is worth it. “Worth it”, for American lives, is around $7 million.
That's a pretty arbitrary number, and it isn't the same for all lives. What's the dollar value of a life in Haiti or Cambodia? I don't know, but I know the US government sure wouldn't spend $7 million to save one.
GiveWell currently estimates that its top-rated charity, the Against Malaria Foundation, saves lives for about $2,300. That's a pretty great deal, considering. In my whole life, I don't expect to earn $7 million. But I do expect to save hundreds of lives by donating to cost-effective charities.
The nice thing is that economies are not zero-sum. It's not just a question of shuffling money around; sometimes there are win-win solutions. Some changes (like immigration) create more well-being for everyone, and we should aim for those.
But in the meantime, it's nice to know that you can save people's lives for a lot less than it costs NASA.