If you have to ask why a cheaper camera is better than a more expensive camera, then you’re asking the wrong question.
is that better? happy now.
sorry, but this is the most retarded comment in the entire thread. check the details and your spelling and try again
Well if you don't understand what the differences are between the cameras then you don't understand the gear. While sure they all can control shutter speed and aperture and have ISO settings, it's beyond those settings that makes the camera different.
If you just look at AF, the 5Dmk3 will run rings around the AF that's in the D600. That in it's self can be worth the money difference. But even if you look at the other things that makes a difference, even the quality of the images coming from the 5Dmk3 are different than what you get from D600. Understanding your gear is one the most important things as a photographer you need to do. If your not getting the correct exposure out of your camera then you need to understand why.
So perhaps that's why the most retarded question in the post is "How is the <$2000 D600 so much better than 5DmIII"