The government has reacted to new Treasury estimates showing that their modified ETS will cost $150 billion by 2050 by claiming the figures are "fantasy" from "Disneyland", and that they do not want to "rip $100 billion out of New Zealand businesses and taxpayers" (implicitly accepting those costings) to pay for it. Which may sound good, but ignores a rather important point: we'll be paying for it anyway - those billions will still being "ripped out" of the New Zealand economy. The only question is how we pay for it: through an ETS, or general taxation. Which in turn means who pays for it: polluters or ordinary taxpayers.
Under Labour's scheme, polluters would (eventually) pay. under National's they don't. Instead, we pay, in order to subsidise the profits of the farmers and industrial emitters who are causing the problem, and protect them from the consequences of their own greed and stupidity. And that simply isn't fair.