It should be, you mean. But it's not. Well, it is in a political sense --- the cost of pushing for policy that will leave you vulnerable to political attack vs. the benefit of being prepared for a bad storm at some point in the future.
And then there's corruption... a different cost/ benefit calculus altogether. Everyone knew that sooner or later a hurricane would destroy New Orleans. If I recall correctly, there was a lot of corruption associated with the federal funds allocated to the Army Corps' attempts to improve the city's flood control system, a project that was inadequately designed, sorely underfunded as it was, and planned over a time table that didn't match the risk at all.