I think you've really hit the nail on the head there. I also grew up in New Zealand and left for Australia for the reasons that you specified. Cost of living is the same or higher than Australia, but with lower wages. My grocery bill is almost half of what it was in New Zealand, my rent is about the same, and my salary is double what it was back home.

New Zealand is a great country if you want what it offers. If I did want to settle down and raise a family I'd sail back across the ditch in a heartbeat.