lokhor: Is there a reason why Aussie ISPs can all sustain throttled speeds greater than 64kbps yet NZ ISPs can't?
One would guess population density.
Bottom line is that no matter where in the world you are, investors still have to make a certain percentage otherwise they will take their money elsewhere.
The rule of less customers brings greater price per unit,
or as the case may be with NZ ISP's; a lower quality service/product to get the price reasonably comparable to the likes of Aussie (or OECD average) - hence 64K cap.
EDIT- Quality may not be the best word, but you get the drift.