Oh absolutely, sunk cost fallacy is a problem. No disagreement there.

However, my point is cancelling a project doesn't remove the need. We need better public transport, we need ferries, we need infrastructure upgrades. All of these things need to happen, and the longer they are put off usually the more they will cost. So it's not so simple as a sunk cost, as cancelling a project then doing it again later may very well end up costing more in the long run than the over run cost of the initial project. Case in point, the ferries.

I will admit, though, I know less about the wellington light rail project. I was under the impression that a lot of the cost being spent was paying for land that was needed for the project, but you can probably inform me more about this. I'll just say, rail is still needed (or some form of mass transit system).