The fine, although still a fine and money to be paid, is not awfully substantial (but likely a huge dent in the wallet for everyday humans).
I'd probably half-expect there may be a countersuit against the airline in light of assault or the minor injuries he's sustained. Then again, as he was belligerent first (assumed), I'm hoping that may deter such a suit.
EK may or may not have blacklisted him by now.
My guess is that for such an offence, they can't legally confine him to the country until he pays up, so they'll likely hand him his passport back. If he leaves, he may not be able to re-enter Australia without paying the fine, but of course he doesn't have to do either.
If they manage to confine him here until he pays up, then who knows if he'll squat here for a while without paying. Not sure if that is ideal. He can't necessarily be imprisoned because that would then be in lieu of the fine, and as far as I know smoking on an aircraft, unless it has serious consequences, can't be punished via imprisonment.