Nine times out of ten when I hear somebody talk about "prestige", they have no experience in applying and getting a job in the world in commerce. It seems to be either prelim or HSC students who haven't even started uni or people with nothing on their resumes who then resort to talking up their university as if it's some ultimate free pass into a job.
Does bias exist against some universities? Yes it does and I'm not going to pretend that it doesn't, especially in the super competitive finance roles. But guess what, people are also going to be biased against you because of your skin colour, the way you dress, the way you speak and so forth. You will never truly escape it. Is this bias wide spread and common? In my opinion, it's hardly as profound as people like to make it out to be (unless, like I mentioned above, you're aiming for something super competitive like investment banking).
Others may or may not disagree with me, that's their opinion and they're entitled to it. I can only base my opinions off my personal experience in finding and gaining work and that of people I know.