They're not enormously complex from a hardware perspective, but the sensing element is really hard to get right. Interference from a whole host of common drugs (including ibuprofen) can really mess up one's signal. Not to mention the regulatory moat; many medical device startups die on the vine working for regulatory approval, or looking for funding for expensive human trials (which quickly get into the millions or tens of millions for a Phase II/III trial)

Consumables -- that go into your body, and hence are expensive to manufacture -- are a big chunk of that cost.

I know this doesn't change your point, but note that it's $400NZD -> ~$270USD.

They are entirely disposable. The transmitter lasts 3 months and the sensors last 10 days. I read something about the FDA requiring the sensors be forced to not work after 10 days, because they were worried about infections.

Interesting, so it really is a subscription cost as well

Medical equipment rules and price gouging. More medical equipment standards for the CGMs. More price gouging for the now $300+ vials of humalog.