That's because they are not yet officially campaigning - not until each party has its official launch. Tony Abbot will launch his campaign on Sunday; Julia not until FIVE DAYS before the election.
And until that time, we're paying for all their transport, accommodation, etc., for themselves and whatever staffers, wives, daughters, boyfriends, hairdressers, et al to take off wherever and whenever they choose. But from the moment they officially launch their campaigns, the public purse snaps shut.
I always wondered why they left it so long to launch – now (thanks, Annabel Crabb), I have the answer.
http://www.abc.net.au/news/stories/2010/08/04/2972709.htm?site=thedrumMaybe, when they have the balance of power in the Senate, the Greens should introduce a bill setting a time limit after the writs are issued for the parties to move officially into campaign mode. They're the only ones who would do it.