They aren't the ones footing the bill, tax payers are
Naive. Taxpayers aren't "footing the bill" either. The national governments pay for their pet projects by expanding the money supply, pure and simple.
And it's likely that a very small portion of the intelligence budgets of the major industrialized nations leaves their respective countries, while a fair bit of money likely enters due to intelligence trade with assorted despots and other foreign parties. So on balance the economic activity due to the intelligence-industrial complex, in the US or similar states, is likely to benefit the populace, in a strictly monetary sense.
But the upshot is that, yes, monetary cost is not the way to create incentives against the intelligence industry. Unfortunately, nothing else looks like a particularly viable candidate either. It's likely to be around until the next civilization-destroying catastrophe. (When the next supervolcano goes boom or a decent-sized rock hits the planet, the NSA will be well-down on the list of things to worry about. Obnoxious as they are, and as much as I'd like to see civil rights restored, there's something to be said for having these sorts of problems.)