There would be marquees, scaffolds, chairs, tables, PA, barricades, facilities like Aero club??, cleaners, several thousand L avgas for some display aircraft, pay for display aircraft and pilots.
Fair bit of travel expense for organizers, (they dont just turn up for the day).
Certain key people would need paying to turn up and work on the day.
All the volunteer help on gates etc take portion of gate fees,
But by far the greatest is Insurance Id guess. An event open to public, council liability requirements, small aircraft plummeting into crowds........can see dollars requested being significant.
I have no real info on this however can see significant expenses.
I would have thought the airshow would be a big consumer of funds but it also get lots to turn up.
Remember this event is the combining of two of three events and still it finds it hard to stack up.
What does that say for aviation in AU and those involved?