It's not hard to believe. I looked up Sunnybank's numbers (sort of the equivalent to GW in QLD) and it was a shocker, I think like 7-8% unemployment. These suburbs consist of Asians that have come over here with heaps of cash but unemployable due to the language and culture shift. I know plenty of middle aged Asians that just sit around sipping tea in their million dollar homes.
You might be onto something.
According to these both have about the same average income with Wezza a little more.
http://glen-waverley.localstats.com.au/demographics/vic/melbourne/east/glen-waverley
http://werribee.localstats.com.au/demographics/vic/melbourne/geelong/werribee
BUT household income for Glen Waverley is over $200pw more. And it's typically households that buy homes not individuals. I'm also guessing Glen Waverley has a more of an older demographic who are retired.