Upload & Sell: On
As a D600 owner, and a rank amateur, I can say that my images do NOT appear overexposed. What I do find is that there is an incredible amount of detail and dynamic range in any image, over- under- or correctly exposed. Maybe that explains some of the difference.
As a case in point, on a recent trip after I had just gotten the camera, I took landscape shots using a bracketing sequence of -2, 0, and +2. As an unscientific evaluation the 0 image nearly always looked exactly like I remembered it. And as another unscientifc test, in ACR, if you use the auto exposure button on the plus or minus bracket it would always adjust close to the 2 ev that it was "out." Generally the range was in the 1.8 to 2.4 range. Given the level of contrast in the images, I would say that these were pretty close.
I vote bad copy of camera.