Well, first note that you have to compare the current costs of scanning to the counterfactual where there is no scanning and terrorists know it. I'd wager we'd have at least a few bombing per year. (Planes seem to be a high-visibility target, and the US gets various random bombings on a yearly basis.) The cost of a downed passenger plane is of order $2 billion, using the statistical value of $10 million per life in the US.

https://en.wikipedia.org/wiki/Value_of_life#Life_Value_in_th...

The TSA's annual budget is $7.5 billion, of which only part gets spent on checked baggage screening.

https://en.wikipedia.org/wiki/Transportation_Security_Admini...

So those are some very rough numbers, but I think they will come out favoring screening. I'd be very interested in the calculation if you'd like to try to be more exact! The hardest part will be estimating the counterfactual bombing rate, but I bet the FBI has expert estimates of this somewhere.

That's a hard sell. I'd rather have luggage regularly stolen outright than perish in a plane crash. Luggage and lives are hard to compare.

I'd rather not die in a car crash, but that doesn't mean I'd pay an extra $10,000 for a car that reduced the risk of dying in a crash by 1%. You can't avoid putting an effective price on life, and in the US it's about $10 million.