Delta IV is notoriously expensive, but USG has plenty of DoD cash for expendable launches in general. The next block (phase 2) NSSL launches are 60% ULA Vulcan. We'll see what phase 3 looks like. I suspect it'll be far more weighted towards SpaceX to try to give ULA a kick in the pants.
DoD and USG learned through the 90s-now how screwy things get when you don't have enough competition or you can't spread your money evenly amongst vendors. They will spend the money now and indefinitely to assure they can get to space when they want to, how they want to.
That doesn't mean they're happy about it though. I'm sure they'd love if everyone was as affordable as SpaceX.
