So: can anyone come up with a cost/benefit analysis, please ?
For the NSA/CIA, the Koch-brother sponsored right wing zealot groups, etc. the cost benefit analysis is quite simple.
Does it benefit the NSA/CIA/Koch Bro groups and their agendas, directly or indirectly, even a little? If so, do it. If not, don't. There is undoubtably a risk analysis component (how likely are we to get caught?) but the general pattern seems to be to do what they like and rely on their ability to destory the reputation of any people of good conscience who stand up against them, much less report their malfeasance.
What is particularly disturbing about this is the lengths to which they are willing to go, the degree of negative-sum activities they are willing to engage in (they don't mind engaging in massively destructive activities against others for very modest, even minor gains, where the negative impact to their oponents, society or the world dwarfs their own miniscule gains), and the degree of silence from otherwise "good persons" who nearly always opt to do (and say) nothing. It reminds me of the old post-WW II adage which concludes "and when they came for me, there was no one left to speak out" (paraphrased).