If I follow your idea, J*' salary's would be crap in EU or even for the Sates, about if you were comparing it with India, Bangladesk, Pakistan...etc ?????? would that be a good salary if you were living in those ****ty countries? you bet!
It's a pointless comparison unless you are actually living in those countries permanently. if you are living and working in NZ, or intend to be back here eventually on a long-term basis, all that really matters is what you pay equals in NZ dollars. The US dollar rate is worth following for contractors, who are usually paid in either US Dollars or Euros, but otherwise it's only use is as a de facto monetary standard of comparison.
I go back to what I mentioned before, you have to come up with a basic monetary value on the buggeration factor of living overseas. On my last contract, I earned shedloads of money but wasn't there when my kids had parent-teacher interviews or needed my help and love. Was it worth it? Half of me cautiously says yes (that's the half looking at the new toys and house extension), and the other half says definitely not (that's the half that mourns the family time that can never be recaptured).
That's the bit you have to figure out. For me, the Jetstar offer looks pretty good, as it gives me the best of both worlds, and the difference in pay is more than made up for by the fact I get to live where I want.
The other point is that decent DEC opportunities in NZ are virtually unheard of. Grab it while you can. If the conditions eventually depress you, move on.