Shit. The fees are approaching 5 grand!!.
For that kind of money you could afford to cross the pond as many times as it takes to build up your experience until you can climb Aoraki without a guide.
I suspect insurance costs are largely to blame, and of course, they generally fly you half way up the mountain anyway, which costs money and robs you of the lower half of the mountain.
Personally I'd rather do Mt Earnslaw alone than climb the top half of Aoraki with a guide. But each to his own. I can understand anyone wanting to stand on top of Aoraki. Enjoy.