I noticed this as well. I guess the question is, do the orders from the US site ship from within the US? If thats the case they will arrive much quicker than an item that has to ship from overseas.
AU: http://www.studioproper.com.au/pages/shipping
US: http://www.studioproper.com/pages/shipping
Orders typically ship within 24 hours from our [sic] of our regional fulfilment centers.
Standard ground shipping (untracked) is offered at no cost on all orders, regardless of delivery destination. We also offer express shipping (trackable) for an additional fee. Express shipping options and associated fees are calculated during checkout based on real time shpping rates.
And they do have two physical addresses, one in Australia, and the other in California. My guess is that they'll ship from the closest region, however, since it's a new product, it might be produced and shipped to their headquarters in Australia first, then their fulfillment center in the US.