I just spoke to Ticketmaster. they are handling the Perth and Melbourne shows. They tell me that Perth 2nd concert tickets are moving slowly and still quite a few left. a 3rd perth concert is highly unlikely coz Sunday is not selling as fast as the first show.
They also told me that Melbourne is totally sold out, but perhaps the reason for the other cities not getting a 2nd show might have something to do with the amount of time it takes to deconstruct+move+reconstruct the stage from venue to venue. there just isn't enough time to add extra shows in between a schedule that is already tight, but perth on the other hand is the last show of the leg so thats why they were able to add another show at the end without having to pack up and be someplace else by a certain time. Dunno if that is all true, but it sorta makes sense. Please don't flame me!! That is just what ticketmaster told me.