Geektastic: What would they do if Amazon just laughed and said “On yer bike!” I wonder?
I would imagine all Amazon packages would be stopped at the border and not released until you paid the GST. There is perhaps an even chance that you would need to personally visit the port in Auckland, carrying three forms of ID, two utility bills and pay by cheque. You will also need to return at least once because it was actually bought using a credit card in your partner's name and your partner hasn't given written authority in triplicate for customs to discuss this box with you, witnessed by a JP under the light of a full moon. Even though your name and cell number are written on the box.
i.e. While no skin off Amazon's nose, Amazon's buyers would have a painful shopping experience. Whereas a box from perhaps Walmart (which has collected GST on Custom's behalf) would sail through unimpeded. Where would you buy from next time?
Amazon is very good about showing customers up front about the likely tax to be imposed by the Gummint under whose dictates you happen to live. Different US States have different rates of sales tax and Amazon has fought and lost that fight previously.
Does raise an interesting query about whether Amazon Marketplace / Aliexpress merchants (individually under 60K) would be subject to the tax.