More than likely similar pricing if you were to hurt yourself in Aus without Medicare and insurance. I’ve lived here for 18yrs and needed an emergency operation in Perth while back visiting. Gallbladder removal. By memory it cost me $11,000aud. Answer from @Jason Wheatley
My understanding is if you missed your 90 days report, doesn't matter one time or multiple times, there is only a one time fine and I see no reason why you should exit the country because of a 90 days report. Please correct me if I am wrong. Maybe someone with better knowledge of the rules can confirm.