The raw files from a Nikon D800 are usually around 38MB each. Assuming similar size, a raw file from the D850 will be 50MB. So, this camera will be able to push 500MB/s? I would be quite shocked if it did.
If it is as good as that, then the price is going to be pretty high. With that level of performance, I don't see it being under $3,999. Damn.