Government action driven by a desire to “do something, anything, about the threat,” as Steven Brill writes in his September cover story for The Atlantic, is expensive, and frequently counterproductive. In the push to ramp up the homeland-security apparatus, America lost sight of the fact that all money is fungible and all policies have tradeoffs. And now inertia has taken over, with a swarm of bureaucrats, contractors, and grant recipients available to administer a nudge whenever the flow of money seems likely to slow.

Virtually all of national-security spending is one massive, overly complicated trolley problem, the brain teaser that ethicists love to talk about when they get drunk together: People will die no matter what the government does. So how should policymakers best weigh action versus inaction?

Brill writes that “it is astonishing that so many hospitals have refused to spend … the $300,000 to $400,000 necessary per site to increase security” plus another “$250,000 to replace a cesium-chloride blood irradiator with an equivalent FDA-approved nonradiological device.” But is it astonishing, really? This looks like a near-textbook case for cost-benefit analysis. Hospitals have a choice: They can spend $300,000 to improve patient care by buying a new MRI machine or paying nurses more, for instance. Or they can hedge against a very unlikely event—the theft of radioactive materials from their facility—in an officially proscribed way that may or may not be suitable for their work.

The right choice depends in large part on each organization’s ability to estimate the likelihood of a wildly unlikely event, never an easy task. But it could very well be true that not taking extra security measures is the way to maximize life-saving outcomes for the most people. It might not be the right call to skip the security spending, but it’s not “astonishing” that some might refuse to do so in favor of other live-saving improvements—or profits.

After 9/11, no one wanted to hear that millions of small knives have safely been carried on airplanes for decades and the prohibition on them now is unlikely to reduce the risk of being on a hijacked plane going forward. Even if TSA security procedures have reduced this kind of risk somewhat, they have almost certainly not be worth the inconvenience and annoyance and lost productivity that has been caused by the process of taking those knives from law-abiding citizens day after day, year after year. So policymaking and spending marched on as lawmakers studiously ignored the tradeoffs.

As Brill reports, in 2013, the Obama administration quietly changed the guidelines for how to react to a dirty bomb in D.C. with little press or public announcement. But he wasn’t neglecting “what could have been an ambitious, gutsy exercise in public education,” as Brill says. He was simply acknowledging the reality that people are not keen to hear that preventing 50 cancer deaths isn’t worth evacuating a major city under emergency conditions. People don’t like that kind of math when it’s a question of life and death. Opportunity cost is a concept that most politicians are smart enough to understand. (They are also smart enough to know that it’s not an easy sell to the general public.)