I listened to an interview on SBL a while back, annoyingly I can't remember who the player was. He plays Alembics and said, quite simply, that he could play things on those that he couldn't play on other basses. Much like the violin bow above, he was good enough to feel the difference between basses and those enabled him to play better.
I am sure he could make my £250 bass sound awesome as well, but I bet he would prefer to take his own bass on a paying gig.