No, we never get to order in AUD, we have to pick a currency, either USD, NZD or EUR. So if your in the US and order say Smaug for $699 USD, then when it ships and you get charged, you will pay $699 USD, end of story.
However, Weta, if they convert that to NZD to put in there local bank account, then the amount of NZD they get, will totally depend on the exchange rate at the time of billing. So given say 6 months between pre-order and shipping, then the amount in NZD that Weta would get from that same $699 USD could be very different, even tho it's all the same to you.
However, since they don't state an AUD amount up front, then over 6 months, I'm totally at the risk of exchange rates. Weta basically still get the same amount, so if I ordered Smaug for $699USD, then Weta will get $699USD. But from my point of view, over those six months, it may have gone from $750 AUD to costing me almost $900 AUD.
Having said that, Weta are no different then Sideshow, QMx or any of the others that don't list a set AUD price and it can take 6 months or more from pre-order to actually paying. For a bit of time it didn't matter, when our exchange rate was almost $1.10 to USD. Now, as we close in on $0.75 USD, it's all starting to hurt again.