@chronicthehedgehog: Keifer did all the facial capture for Big Boss. So he was there regardless of whether he was talking or not.
I've been wondering how this process worked. He would have had to do the facial mo-cap for all of his delivered dialogue. But, what about scenes were he isn't speaking? Did they have a camera on him to capture his performance for every cutscene? Part of me thinks, that there has to be some of this that was recycled.
Kojima has said that his favorite film is "Mad Max 2". In that movie, Mel Gibson has something like 10 lines. He really just doesn't speak. There was an interview with him and Keighley a few years back where he remarked on wanting to tell a similar story. This makes sense to me, because Max spoke more and had a different demeanor in the first Mad Max film. By the second one, he'd experienced pretty traumatic loss, and watched the world go to shit around him. It's a pretty similar character arc to Big Boss.
I'm sure Keifer's time really is quite expensive. But, considering the scale of The Phantom Pain, I'd be seriously surprised if Kojima was willing to sacrifice Snake's dialogue purely based on the cost of the talent.