We bought a dinner set from Macey's US (despite some pretty horrific reviews for service on resellerratings etc - they were the only on-line direct supplier of what her indoors wanted, and not available locally. Macey's more upmarket sister company Bloomingdales will not ship to NZ, so that would have required use of a re-shipping service).
They offer an option of guaranteeing delivery with GST etc "pre-paid" through their export agents "Borderfree" who use DHL for air-freight to NZ. Total cost was about NZ$1200. The cost they calculated for pre-clearance was about the same as what the combined GST and ITF fee would have cost.
They staggered shipments, individual cartons of <NZ$400 each shipped and arriving about a week apart. Documentation I received with each packages gives no clue as to whether GST was in fact paid. I doubt that they did. I don't know - it could have just been a stock availability issue from their warehouses - but I suspect that they are on to it - making "pre-paid clearance" attractive, then deliberately staggering consignments to Aus/NZ to avoid respective GST thresholds in each country.