Ann: Definitive Feasibility Study Presentation, page-29

I’m a simple sod and reckon the workers want to be paid in A$, the truckers want $A, the office staff want A$, the government want $A etc. Nobody gets a pay rise when the exchange rate moves.
I reckon the primary currency for costs for an Aussie project is $A.
The value in using $US dollars is with the global cost curve but the use of different exchange rates by the peer companies means that comparisons can only be made in $A on costs, IMO.