The tour I did included the your part of it too. I found meals were slightly on the expensive side (compared to food in NZ), but I think my UK buddies found it reasonably priced. I guess it depends on what optional activities you are planning on doing while there - I did as many as I could - make the most of it.
I can’t remember how much everything cost me but I was in Oz for a month & all up, all flights (NZ return & Oz domestics, trip, food, optional activities, I think it cost me around $8000ish NZD.
Dont know if that helps at all, but when you take the price of the tour & about $1000 in flights off, hopefully that gives you a vague idea. This also included my $600NZD skydive (Which I would totally recommend because it was so awesome to do that as a group!)
What I would suggest is to buy snacks for the bus from a supermarket before you leave town. Some of the places you stop in are small isolated stores that will charge you about 4x as much! There was one store we stopped at where a packet of chips & a pack of gum was $7!!!
Sorry, not really sure I answered your question…