Aredwood: They also (in the USA at least) have a supplier diversity program. Which helps smaller suppliers get their goods into Costco stores. https://www.costco.com/supplier-diversity.html Which should be a great help for the many small companies in NZ.
I'm always a bit suspicious when supermarkets no longer stock a perfectly good NZ made item. Lately it's been bothering me that more and more shelf space is being dedicated to overseas made no brand cheapo products. I actually doubt many people are buying those but the supermarkets want to increase margin and pressure local suppliers.
I doubt Costco will save all those maybe one or two.