You are correct, if you use current exchange rates the capital...

You are correct, if you use current exchange rates the capital cost is around AU$580M, not AU$638M as I suggested.
But if you also use current exchange rates the revenue isn't as high is AU$.

The bulk of this project is civil engineering done in Australia by Australian contractors who get paid in Australian dollars. The exception is possibly plant, power and harvesters. But remember they do not intend funding the power, we don't know who is.
A large chunk of the debt (if successful) will be NAIF funding in Australian dollars. I bet Savich has a spreadsheet with $638M Australian dollars as him bottom line number and has applied the 0.65 exchange.

The US$500/T is what companies making conservative assumptions have used from the start (there was only one at PFS level).

The haulage is easy. Remember this is the most remote SOP project in WA and they have to build almost 400Km of their own road.

The problem for them is that their -15/+20% DFS @ AU$638M looks very expensive compared to the RWD -20/+20% PFS @ AU$451M (with a bigger contingency).