Geektastic: Whatever they charge is still too much given the amount people have to pay for telecoms and interweb in NZ in the first place.
I am also enraged at being overcharged for beauty products and salon services in NZ, but that has no relevancy to this discussion, I believe.

There's no personal intervention until way way beyond a few months - it's all automated text, calls and disconnection which does not cost $10.
Disconnections do cost us. Physically disconnecting a line always involves getting a Chorus tech out, and we have to bear the cost of this.
Far better to offer $10 off for paying on time - a much better image.
I cannot speak to why Vodafone chose this route, but let us not insult the average Kiwi by implying that a discount for paying on time is anything other than avoiding a late payment fee.
Speaking as a consumer from my own point of view, if I am paying late, I am paying late and should be held accountable for not keeping to my end of the bargain. If I am not paying my bill on time, I am withholding funds the service company is now unable to use towards their cashflow and I should be penalized for doing so. It is simple economics, yes?