The budget was very high. They got two real actors to voice the parts and act the scene with mocap. They had mocap for facial espressions. They also had a famous person do the soundtrack.
My question to this though is... why the hell did they set the budget that high? I mean I bet the voice and acting from just those two people took a good chunk of the budget. I bet they seriously could have cut the costs in half and still have the game just as enjoyable.