I ended up paying about $450 for mine, can't complain as it was convenient and if I had any problems they could be fixed locally (TWOC). Have since bought a couple of kegs from ultimate air.
Try TWOC (probably where you did?) or try Ultimate Air in Osborne park (you will probably need a seal kit to fix their kegs as they are as-is). I am sure there are other shops that sell them as well.
Beside that if you search for Kegs from the US here you will see where you can get them via ebay, 12week wait but perhaps cheaper. Get your reg in Aus however as I think the yanks have different threads etc.
Hope that helps.