This is not about mastering, but on topic nevertheless.
I remember back in the old Swemix days (that is, before Denniz Pop left and formed Cheiron) when Denniz Pop and Stonebridge worked together producing and remixing. This was some fifteen years ago or so. Cheiron had just begun their way towards fame.
They both kept dreaming about one day getting their hands on the original master tapes for Chic, and how great that would be. They'd even do it for free, just to get to lift stuff from the tape for their own private pleasure.
One day I was at this party at Stonebridge's house, and he was so revved up because he had finally managed to score a deal to remix and get hold of those tapes. He couldn't wait to tell Denniz Pop.
The minute Denniz Pop and Max Martin walked through the door, Stonebridge told him. Denniz first response was "do I get any points?". Stonebridge replied "No, but man... It's Chic! The master tapes! Oh dude, our dream come true!". Denniz just kept saying he needed points to do it.
Stonebridge was very crestfallen that night, over this. Denniz Pop was one of the most wonderful personalities in the business, God rest his soul. So this was not at all expected.
It all cleared up after a magnum bottle of wine and a lot of singing the lyrics of Dr. Alban "Choosing BPM is a big problem".
In the end I think we all would like to work with someone we dig bad enough to do it for free, but in reality when that day comes it's probably going to be because they value your job and will pay for it.