In reply to aln:
This is from the letter to Nirvana that I mentioned above, about what they should pay him;
"5: Dough. I explained this to Kurt but I thought I’d better reiterate it here. I do not want and will not take a royalty on any record I record. No points. Period. I think paying a royalty to a producer or engineer is ethically indefensible. The band write the songs. The band play the music. It’s the band’s fans who buy the records. The band is responsible for whether it’s a great record or a horrible record. Royalties belong to the band.
I would like to be paid like a plumber: I do the job and you pay me what it’s worth. The record company will expect me to ask for a point or a point and a half. If we assume three million sales, that works out to 400,000 dollars or so. There’s no f**king way I would ever take that much money. I wouldn’t be able to sleep."
Gives a measure of him. I really recommend reading the whole thing.
It's a cliché to mention that he didn't consider himself a producer but a recording engineer. An expert in microphone choice and setup. And all the rest of it.