If you think about it, you'll remember that we often hear about how becoming famous tends to 'change' people. Thus what 'Showbiz' is about.
Showbiz is the entire commercial world in a nut shell. It controls you in the first place, then forces you to become the darkest part of you, the very thing you've been trying to control from the beginning. It turns you into a self-destructing machine, something so close to its feelings and to itself that it could go insane at anytime.
And just when you think you're about to loose it, 'showbiz' sets you off again, on a trail that is not yours, change you and shape your public image so that the image that people out there have of you isn't YOU anymore; it's the person that 'showbiz' has made you into.
I think this song is ultimately about how 'showbiz' doesn't change 'us' exactly, but rather the way we are seen and portrayed to the public. And about how that pressure can make someone suffer so much they'd want to die.