Considering john the ripper has a plugin that can churn out 50k c/s on a gpg key with a mid-tier GPU without specific optimizations, I'd guess a dedicated team of NSA researchers could get the cost for off-the-shelf hardware down to 5000 c/s/$ (based on a $100 GPU running 50k c/s + 10x speedup from engineering effort and specific optimizations), which makes the cost of the raw GPU hardware for a 1 trillion passphrase GPU cluster a smooth $200 million for a civilian assembling in his basement.
Wanna bet the NSA gets volume discounts from nVidia/AMD?
Wanna bet the NSA gets volume discounts from nVidia/AMD?