I agree that PP a RAW image can give amazing results, and I shoot raw most places so it gives me that chance if I need, but having seen a few wedding albums and the amount of images in them, there is no way they can PP them all individually - it would take literally months correct exposure, white balance, sharpness etc. I'll be interested to talk to a wedding photographer when my time comes to see what PP they do and how much time they spend per image. I agree that if they put a lot of effort into PP then £2k could be a good deal.
Also, not sure how you can gain back dynamic range in PP. A sensor has a finite range of values it can sense. Once you go over or under them, there is no way to get them back (lets forget about HDR for now as that doesnt apply here). No amount of post processing can get you any more darks or highlights once they have been lost. I guess what you are really meaning is that you can shoot underexposed so not to blow the higglights and then up the exposure in PP to bring it back to where it should be but without the blown highlights?
As said, I'm difficult as a customer, as I'd prefer they didnt do an PP and just gave me the RAWs but they would never do that, as I am cutting out some of their work/time which they would want to bill for