LUCKY-1
You will be the LUCKY-1 to get anything that makes sense from anybody who actually knows the answer to your question or at least is willing to share it with you for free.
May I suggest the most accurate answer you will get will be by subscribing to the likes of say Concklin de Decker Associates who will for a fee provide an accurate answer based across a broad cross section of the US experience, which, when you apply the appropriate exchange rate, fuel and labour rates will be more or less the Australian answer.
The fact that they might not agree with the local sages does not mean that the figures are incorrect it just means the local sages might need to take a closer look at what and how they are doing it.