I suspect the NSA doesn't care too much about bang-for-buck. 22nm FPGA's [1] seem like they would work pretty well.

In an interesting twist, The Register claims that Achronix's decision to use Intel was driven in part by national security considerations. We've reported extensively on the idea that chips fabbed overseas in insecure facilities could contain hidden kill switches or backdoors that would let an opponent cripple the US military, and Achronix allegedly wants to be able to sweeten its pitch to military customers by offering a home-grown solution.

[1] http://arstechnica.com/business/news/2010/11/intel-shifts-st...