I'll start with a proviso that I've only ever worked and lived in NZ, but have visited a lot of overseas countries and looked pretty closely at their living costs.
I agree that it is not cheap to live in NZ, but I don't think it's as expensive as a lot of people make out. Bearing in mind the exchange rate, a typical grocery shopping expedition is similar in price in NZ, the UK or Australia, and not much more than the US. Even Hong Kong isn't cheap if you shop at the western type supermarkets (but look at the cost of accommodation!) Lots of products are swings and roundabouts...less for some things but more for others. I live in Auckland, so housing is expensive if you want to live somewhere nice, but nice suburbs are expensive in other places too. Cars used to be very expensive here, and new ones still are, but 5 to 10 year old used cars are really cheap. Education is cheap and the State schools are pretty good. Private schooling is expensive, but that's a luxury and not a necessity.
The exchange rate against the UK pound was always around 33p to the NZ$, but it's now around 50p, so no wonder it's tough for kiwis who want to return from the UK.
With regard to the "average wage" of around $50k, most "airline" pilots are on much more than that, and most GA pilots would be close to it. OK, you are not going to earn much as a basic C-Cat instructor, but you never really did, even back "in my day".
Like any country, there are expensive places, and cheaper places, with the big cities being the most expensive. Life is much cheaper in rural areas, but that is not always an option for folk in our industry. It all depends on what you want and how you want to live your life.
I wouldn't want to live anywhere else, but nothing is for free....I'm sure I could make more money elsewhere, but that's not the aim of my game.