I think my previous reply to the OP was very confusing.
So try to rewrite it here:
IIn many ways the Sony A7R is not as refined as the D810 is , but it is a lot less risky and also much cheaper to get.
And if you do shoot only landscapes or studio set up work , then there is no difference between the D810 and the A7R.
36 MP would be nice but also will increase workflow (larger files, more disk space, longer processing times, ...)
Don't worry about that, it is not true.
My first digital camera was a 1.3 megapixel one (a Canon/Kodak DCS 3C).
Now I have a 36 megapixel one, and imageprocessing is about a 1000 times faster.
The rate that computers are becoming faster, (and the harddisks are becoming bigger) is much greater than the rate the camera's get more pixels.