The US figure is only a trigger to do the appropriate study.
In the USA the equivalent airspace would be class D and thats what AA want here
However CASA can't move on from the 1950's so thats why they are saying class C.
Of course Mike Taylor could fix the impass in a minute- He is clearly the person responsible because he well knows CASA won't make any decision which offends Qantas.
And it's not about who is prepared to pay for the manning of the tower-it's about what is necessary for safety.