kiwitrc: Since you mention vote buying, the TaxPayers Union have a Bribe-o-Meter on their site showing how much tax payers are going to have to pay for the promises of the various parties. Currently only the Nats and Labour are up and they say they will add to it once policy is announced.
The TaxPayers union are an unashamedly partisan right-wing group and as such any information they publish should be treated with a grain of salt.