The price difference between the D810 and a Sony A7R II is 5%, so for all practical purposes same price in Norway. 5% amounts to about 175 USD, i.e. quite a bit less than "several houndred dollars". Considering that the original first gen Sony A7 is full frame, it's one heck of a deal right now, if you can live with some "plastic" parts. Full frame doesn't get cheaper than this right now. Btw. I don't think sales figures for individual camera models are publicised.
I, as already known, much prefer EVFs, but that is not the subject up for discussion, rather build quality is. The first generation A7 uses plastic parts and is cheap, so you get what you expect. The expensive A7R II uses a metall construction and you again get what you expect. If I had liked OVFs, the D810 would look like a great camera for me, and for the price I would expect it to have a metal construction, particularly the supporting structure around the lens mount. I really thought that the D810 was just an update to D800 electronics + fixing the bottom frame structure.
Sony surprised me by seriously enhancing the build quality of the second generation A7 models, though they still have a way to go regarding the user interface. I did not expect to see Nikon change the build quality the other way around going from metal to "plastic".
If Nikon releases a mirrorless FX format camera in the future, better build quality than Sony would be a key factor for luring me away from Sony.