An LNG terminal wouldn't help with cost (it would probably increase it a bit, if anything, as the cost of building it would have to be paid back). It's desirable from an energy _security_ perspective; as it is we are very dependent on a pipeline to Britain.
Actually it should help with both, because a on-island terminal would also provide LNG storage capacity which would buffer short-term price fluctuations. We have zero such storage.
Again, our poor decision making around national infrastructure is on our governments. They left have left us completely exposed to international markets.
A lot of it relates to the planning process, they do keep trying to build things. One could argue that this is also their fault (and I do!) but there are good historical reasons (cough ray burke cough michael lowry) why we've ended up with such a bureaucratic, byzantine planning process.
Yes, there are many problems with the planning process, but as you conceded in another comment, the actual reason that we don't have an LNG terminal is that Eamonn Ryan nixed the possibility.
As usual with the Greens, perfection was the enemy of the good.
Yeah, even though I voted (happily) for the Greens, I was very disappointed in them not building an LNG terminal, purely for energy security reasons. I'd be super happy if it never got used, but it's a cost worth paying just in case.