If it saved just one life...

... it still might not be worth it.  There are myriad ways we can reduce the probability of injury and death.  We could lower speed limits to 25 mph.  That would go a long way to reducing traffic fatalities.  The benefit of any reduction in the probability of injury or death has to be weighed against the cost.

So spending lots of money on storm shelters for school children?  Probably not the best idea.  Doesn't mean there is no response at all.  David Johnson at The Daily Beast lays it out.  Pull-quote...

building shelters for everyone in Missouri at this rate would cost $6 billion. Based on Missouri’s average of two deaths per year from tornadoes, this measure would save 100 lives over 50 years at a cost of $60 million per life. Even if the shelters last 200 years, the cost would be $15 million for each life saved.