Please note that Israel does not do cost benefit analysis. The other key principles are:
1) Everybody gets screening interview. Do not rely solely on technology.
2) Everybody gets a screening interview. It doesn't matter if you look like a 90 year old Chassidic grandmother, you get screened like everyone else. And security people are instructed that if terrorists can slip by you because they know you give 90-year old Chasiddic grandmothers a break, they will disguise themselves that way. Then you send in some of your own people disguised as 90 year old Chassidic grandmothers to see if they got this lesson. Fire the ones who didn't understand that you screen everybody like a potential terrorist -- which means polite but alert and looking for key indicators.
I always tell people that not only is racial profiling bad for all the obvious reasons, it's bad security!