I'd be interested to know how to estimate things that are very rare or don't have a normal distribution. For instance, let's say I have a bold plan to protect

I'd be interested to know how to estimate things that are very rare or don't have a normal distribution. For instance, let's say I have a bold plan to protect us from meteor strikes that will cost $100B. How would a person make a decision about whether that's a good trade-off or not? And how would a mathematician help them make that decision? How would it change for more complex cases, like a shield to prevent nuclear ICBM warfare which has never happened, but we all are worried about?