It would depend on the airline and what their policy is with luggage.. Im taking pretty much all my gear in a boardbag, boom dismounted, mast, board..(yeh and all my gear is 1 of each item i just mentioned) the mastbase, boom clamp and small bits go in the suitcase and the sail is it its bag by itself. Did that twice, no worries

Having recently read the policy on the Qantas web site, it's not always free. Depends on where you are flying, etc. Here is the link (www.qantas.com/au/en.html).

Alx,
I would recomend renting gear here in Greece, as there is new gear for rent at all popular sailing spots (not so expensive to rent or to buy). Bringing gear with you could be a hassle.
Having done the trip a few times, i can say, you can get away with a boardbag under 30 kg. If you are overweight and in Perth Airport, you are in deep. Things are different in Greece. You dont get away very easily with Thai Airways. They will charge you minimum charge of 5 kg (15euro per excess kg= 75euro) but will not really mind if you are 5 kg or 100 kg excess, as long as you've got it all in one bbag.
Emirates on the other hand is cooler. You might get away for free. But they could also kill you for overweight. And there is not much you can do once you are in a foreign airport with heaps of stuff. Personaly, i've flied with them once and did not pay a single $ for 30kg of equip.

Still i recomend renting stuff here in Greece, as it sounds scary moving around your equipment from the Airport to the Port, and around the islands, and probably paying storage rates to a surfschool. It just aint worth it!!
Hope this helps.
Cheers

By the way, you wont be needing much clothing here in Greece, so travel light. It is allready reaching 40C's, the hottest June i can remember.