They are about $US 15 when you renew them I have found from godaddy. You can buy .nz domains from $15 if you google nz domains if you are just wanting cheap nz domains. You can even get maori.nz ones for just $1.
I suggest you pop over to Whirlpool (www.whirlpool.net.au) and have a read of the constant stream of complaints about the Australian based company you are referring to. (note - this response has nothing to do with the originator of this thread).