This week's AutoWeek magazine estimates the 645Ci at $68K. I would love to have one, but I had heard it would be in the 60's, so I went with a 330Ci instead.
The 635 will obviously be less, and I heard that the 630 will be an "economy" version. Probably still in the high 50's, I assume. That's a lot for a car that could be somewhat underpowered for its weight.