Oh Dear.... You kind of left yourself open on this one. Why are you actually breeding? I have to agree with Cleasanta and AussieFloyd on this issue.
If you sell the pups then they are no longer yours. You did agree to sell them to a good home.
I personally do not see a need for you to breeding your amstaff x as there are so many abandoned cross bred dogs such as staffies/amstaffs/bully varietys/ridgebacks etc....list goes on - across Australia. Many organisations such as DABS for instance are advocating getting pets desexed to alleviate so many animals PTS in Australia. You may not realise it but you are encouraging this population.
I sincerely and honestly recommend without being nasty - that you visit a local animal shelter and have a look at how many dogs are in there. If you visit a "no kill" shelter ask them how long dogs have been there waiting for a home? If you visit a local pound ask them how many dogs are PTS due to simply being dumped or abandoned..... You may get a rude shock....the statistics are very depressing.
There is nothing wrong with Breeding - if its a pure breed and its for temperament, soundness, consistancy and showing or agility or the like.
Perhaps you should consider investing some money into a breed that you like and become involved with the club and meet like minded people with a genuine interest in that breed. You obviously enjoying breeding and raising puppies and want to find them good homes. Please - just do it the right way....