When we were planning our family snow trip last year we also looked into NZ and it came out a fraction cheaper than NSW, but seeing drove to NSW and stayed in a house with a kitchen which also gave the benefit of being able to cook all our own food. So when we added up what a week of buying 3 meals a day and the cost of 4 passports, for us it worked out cheaper to do NSW.
Without kids, then NZ or Japan would have been the go.