Welome to the forum Dharmin.
I'm not sure a NZ immigration forum is quite the place to ask about the cost of living in Oz but
here you go .
This is the closest I can get for
Wellington (or rather Auckland which could be quite similar) . Most of the stuff for NZ is well out of date so there wasn't much point posting it. There's a similar page on here for Perth but it's a year out of date so I put a different one on for there.
If your really want to go into the subject you can look on
here but you have to pay to view.