1) If you are bringing it on a "transfer of residency" exemption from outside the EU, it should be a no brainer that you bring it to Ireland based on the numbers. However, your calculations should involve more than price of the car and tax savings. I've tried to lay out below how I tackled the issue.
2) As one poster said, make doubly, triply, and quadruply sure you qualify for this exemption. Revenue has loads of info on this. Call them up, too; they're quite helpful.
3) If you do qualify for the exemption, there's a lot of paperwork (mainly documents to prove you lived outside of Ireland) to submit to Revenue. It's quite a process, but usually well worth the effort.
4) The easiest way to make the final decision is to do this is to consider each of the following:
a) think about what kind of car do you want to drive in Ireland (if it's the one you have now, that's easy!);
b) see what a comparable car costs here, both from dealers and private sellers (you've done this);
c) see what all the other costs of bringing it over (shipping and insurance, etc.); also remember you can bring in other personal effects besides your car if those also qualify for the exemption;
d) check with a car insurance company here to get a preliminary quote for the car, so you wont get shocked after it is already here;
e) also, check the annual tax on the car (again, to avoid a rude shock);
f) factor in any NCT related costs to make the car legal here (usually not much, but you MUST do this!!!)
After doing these (and you've already done the major part of this), I found that it made great financial sense to bring my car over here. Even with the cost of shipping from the US, which was about US Dollars $2300 a couple of years ago, I came out far ahead. I have a much nicer car than I could have gotten here for a far better price.
5) Arrange for a reputable shipper to move the car over (and ABSOLUTELY get insurance!!!; my car was damaged in transit.)
6) Make sure that cars from Australia will meet the Irish NCT standards with no or minimal effort/work. If your car is 4 years old or over, you'll have to get it NCT'd fairly soon after you bring it over.
7) For the NCT, don't worry about stuff like different indicator lights etc. You will have to get them sorted for the NCT here, but generally, any good car electrician can get it rewired for any configuration for not too much.
8) You might want to talk to some dealers here to make sure that they can service the car. I'm sure they can, but there are probably variations (there definitely were in the US configured car). As much homework as you can do will help out later.
S