[uptown]

Even if cost ever became a problem, at some point the value of the information they're able to unveil would pay for itself. Think of the raw value of having advanced knowledge of confidential business and political dealings. What could that be worth?

[Phlarp]

Makes you wonder how many black ops they could fund through insider trading. Even without specific encryption breaking hardware the scope of NSA's programs would serve equally well to front run essentially any major market move.

How easy do you think it would be to scrape a little cream off the top of the HFT latte when/if you could see everyones source code and/or tap the ingress points on the exchanges?

Even precluding outright "cheats" like above, I can't imagine it'd be hard to beat wall street at it's own games. Prop firms like to buy satellite images of Walmart parking lots and count cars to extrapolate earnings, sounds like a technique the NSA would be in a position to improve upon.