All of our dogs have been bought on main register, including the first two who were purchased as companions. It does depend a lot on the breed and the breeder, or did back then. The two dogs in question were bought for $450 and $650 so it wasn't about charging a motza.
Breeders prefix listing, it depends a bit whether the Dogs SA listing is opt in or opt out. If breeders have to nominate to be listed, well I haven't nominated to be listed in the DogsNSW journal because I figure most readers of the journal will already have a view if they are interested in my breed. My advertising to the general public for companion homes is my website and DOL listing.
I do know a couple of breeders who make a selling point of the fact that they sell unrestricted on the main register, ie, other breeders will ask you to comply with conditions, I won't, buy from me. Each individual has to work out what they think about that, I think there is a happy medium between "I don't care what you do with the dog" and "The dog is not to take a shit without my say so" and most breeders don't sit at either extreme.
Thanks for explaining about the prefix listing, that makes complete sense. :)