Not sure but my guess it is more art than anything. Goes back to the discussion Toe and I were having yesterday. I think it is a combination of how much crowd noise is mixed in and the different environments (studio vs home) that is in play. For concert discs it is 90% about the audio for me. If the audio is great I'll put up with subpar quality.
For any other Nine Inch Nails fans, I go back to "the gift" example which was leaked professional HD footage from multiple shows and angles along with sound board audio. You would think you could create awesome video and audio quality with this. Fans that work in the music production industry went into studios and assembled a Blu-Ray on their own time. While it is great to have and was free, it is very average quality. I probably watch the official release of Beside You in Time 50 times for each viewing of the Gift. Why such a large discrepancy in both audio and video quality is beyond me. My guess is the true Pros just have the art down better. Or that different mixers and mastering engineers have different tastes in how they want things to sound..
I agree and again when mastering loudness is not a substitute for getting it right