I'm learning to approach such SWAG discussions filled with "golly, we just have no idea" by computing outer limits to at least establish "it can't possibly get

I'm learning to approach such SWAG discussions filled with "golly, we just have no idea" by computing outer limits to at least establish "it can't possibly get any worse/bigger/costlier than $X". In this case, I was responding to "You might as well throw out any number" by throwing out a ballpark figure for the absolute worst case audio surveillance cost scenario: everyone, all the time. OK, so the final number is really huge, and doesn't take into account the many nuances you mention...but I know that reducing storage costs by orders of magnitude will leave plenty of room to accommodate your real-world details. With that sweeping overgeneralization, I've concluded that whatever the details of implementation and whatever the extent of monitoring desired, the cost is well within the operating expenditure of the US federal government. Now that we know that it's not realistically going to cost more than 5% of gov't spending, we can contrast that with the NSA's actual budget, and guesstimate how big the eavesdropping effort really is from that. If nothing else, it's an exercise to explain to common readers (not you, you're a telecom guy who groks this stuff) that it IS in fact possible (not easy, not cheap, but indeed practically possible) to record every phone call. The scale of capability of some modern technologies is otherwise incomprehensible to most people; they'll dismiss the notion out of hand unless you can quantify it in very simple terms they can instantly grasp, like "recording everyone 24/7 would cost no more than 5% of federal operating costs." Kinda hard to mentally keep up with technology which has expanded a billion-fold in capacity in just 3 decades.