Ermz: not really. I'm not sure if Jan lives solely off of his mixing/mastering work but he is definitely the guy who does the most production work for other acts in the whole industrial scene. Far behind him in terms of volume of work are Kolja Trelle (Soman), Sebastian Komor (Icon Of Coil/Komor Kommando) and Krischan Wesenberg (Rotersand). For a list of Jan's work go to:
http://www.x-fusion.com/xmp/index.php?content=referenzen
Jan is known for getting very loud and punchy harddance mixes and he works/worked with every label out there. That's why literally every harsh-electro band that is about to release an album made in Fruity Loops is contacting him for mixing as soon as they feel "ready". What's amazing is the fact that his studio is HORRIBLY set up in terms of acoustics (check out:
http://www.x-fusion.com/xmp/index.php?content=samples), but if it works I'm the first to disregard all the acousticians
I dare say his work sounds very very similar from band to band, but so does CLAs, and that's why bands come to him.
A lot of his work is of older date though, so I'm kinda thinking that he's working less than he used to. Also remember: Germany in the 2000s was the mecca for goth/industrial. It's very hard to make money off of harsh-electro anywhere else, especially now, because the only two bands that anyone still gives a shit about are Suicide Commando and Agonoize. There's a German hardstyle influenced duo called X-RX who are popular in the teenie demographic but they don't make money, they're just hip.
I think I'm one of the few who makes a decent income by doing it all myself, but I still wouldn't give up my dayjob ...