My PoL from an overseas online store will be hitting mightly close to the AU$1,000 mark (threshold for GST) when a big ticket item becomes available later this month. Does anyone actually know how Australian Customs calculate the AU$1,000 value? I do not want to pay the GST for being just over the threshold just because Customs may use a different calculation method that I'm not aware of.

Do they use the exchange rate on the total value of the purchase at time of shipping (aussie dollar has dropped in recent months )? My earlier purchases in my PoL have been with a higher Aussie dollar.