When I used $10K/hour for the "average" aircraft, I had in mind the EMB-120 (Embraer Brasilia).
Given W.A.'s present (and recent) FIFO circumstances, I think that that aircraft would have to be at about the "average" point.
A small amount of FIFO is done with C404 and more again with C441 and B200. A lot is done with DHC8/Metro/Brasilia. Bigger again are the F50, BAE146, F100 and B717. B737s are used a couple of times per day to Karratha and at least once per day out to Kalgoorlie. Admittedly, not all pax on the large aircraft would be FIFO travellers (most would be, especially re Karratha).
So, would the EMB-120 be about "average" for the purpose of these calculations? And would it come in at about $10K per hour (incl fuel and crew)?
The more I think about this, the more I think $500 million is conservative. And that doesn't include the FIFO flights into W.A. from other states.