Deeper buffer is always valuable to have tucked away even if you only need to call on it from time to time. Particularly with my 5DIII and less so with the 1D4 I tend to hit the buffer limit at the most frustrating moments...at a peak moment during an action sequence, or worse, while shooting aerials where there are limited and expensive opportunities to shoot the target subject. Sometimes for action I'll reluctantly choose mRAW simply to access deeper buffer.
Because of the almost infinite different shooting styles, some photographers will never come close to experiencing buffer limits. But for others it can be confronted on a daily basis, and needed to be managed...usually at the expense of unbridled creativity. So yes, I would pay $$ for deeper buffer. That might simply mean upgrading to 1DX.
-pw