wow... I want a wet nurse! But it kinda freaks me out too!! I don't want my baby sucking someone else's boobs! lol..

So if it is $50 a litre then they wouldn't get paid very much a day!
I guess it depends on if their employment is strictly as a wet nurse, where Mum is not feeding bub at all, or whether they are providing an extra service as part of childcare. If they were getting childcare rates plus the bonus for wet nursing it might be ok.

This sounds like I'm making a joke but I'm really not - what about nipple injuries? Would that be covered by Worker's Compensation, if the baby wasn't attaching properly and caused split nipples or mastitis etc?
Maybe this would come under OH&S, where the employee has the responsibility to pay attention to safe work practises such as being aware of attachment, and maintaining their equipment (being conscious of blockages etc that can cause mastitis).