I dont think any airline would pay the taxes for you, even if the flight was free. So I'm thinking thats at least AUD$120 one way for SYD-AKL before QF/VA/NZ give you a great deal on a middle seat next to the loos.Staff travel was largely ruined under the last (or is it still current) management. I can still access it, right up to first class, and I even have some long service (i.e. free) flights left. It's such a good deal that I'm looking at forking out $8,000 to Singair.
It's not 10% of the fare either. It's a percentage of a random number that they made up, that they call the fares. If it works, it's good value, but you don't need to be delayed for very long, for the accommodation cost (and probably flights on another airline) to offset any potential savings.
(But if someone wanted to offer me QEA travel companion, I wouldn't say no)