Hello @Anonymous,
Not sure of the details like sales tax etc., in New Zealand but that does seem like you get a lot less than I'd expect.
There's a, short, explanation of some of the things that influence their host charges in the article below. They also charge a 3% currency conversion fee where applicable.
You can see their breakdown of the payment by clicking on "Your Reservations" and then "Print confirmation" for the reservation in question. If that doesn't explain it then contact Airbnb support.
how-do-i-calculate-my-payout
Contact-Airbnb-A-Community-Help-Guide
Steve.