Cost per shot including the development and unit costs amortized over the service life of the weapons system? Or is that just the cost of the energy that got pumped into the laser?
I also can't find the accurate time to target stats, just overall dwell time.
However, they have 100 of them (so spend 4mil). so you might have to spend (if say 100k each). 10mil to protect your 10mil in property (and more if the interceptors cost more).
If on the other hand you can get the cost down to pennies (minus R&D costs), this is no longer part of the calculus.