Hi Charlie, whereabouts in Australia are you, and how much do you already know about RTBs?
I'm in Victoria, and the samueli subspecies can be as low as $1200, whereas the naso subspecies can get up to over $2500 for a good bird.
A well trained black 'too is gentle, reasonably quiet and very affectionate. When they get hormonal, males can get a little over-excited, but in my experience excitation usually manifests itself as strutting and displaying, rather than biting. Females get hormonal too, and can be a bit moodier than males during breeding season, but again I've never been bitten.
Training is very important for a RTB, you'll want to make sure you teach it to play independently.
Black 'toos love to chew things, so making sure you have plenty of native wood around will keep your bird happy as a lark
It'll also need a bit of 'out-of-cage' time to flap around and stretch its wings.
They don't tend to pick up many words, but training behaviours is easy enough.
You'll find that they're very similar to your galah, although perhaps a little more cuddly, if your galah is anything like the ones I know
I'm happy to answer any specific questions you might have
in the United States where they're seldom seen in aviculture.
