Why is dentistry so expensive and low quality in NZ?

I am gluten intolerant which causes soft teeth so I have seen a LOT of dentists. Some of the work is what I needed, and I had to get everything redone 2-3x to fix bad quality work. One of them accidently put a filling on the wrong tooth that had no issues, and I had uneveness on the bottom of one tooth so he just shaved it with a drill without asking and said I got a freebie.

I recently went overseas and I received dental treatment that was a fraction of the price, but also there was no pain experienced with getting injections, and no fatigue the next day from the anaesthetic. They cleaned my teeth for around $20 with warm water so they weren't sensitive. And I got crowns for the same price you can get fillings in NZ.

I'd also suffered from TMJ for the last two years, and it was from having a crooked bite from fillings which hadn't been shaped properly and they fixed it.

The overseas office was also more state of the art, with higher quality equipment than NZ and better quality crowns available - NZ dentists just give you one option when there's many with extended warranties.

Why are they more expensive here for lower quality work?