There are a variety of visa services and they can be useful for countries like Brazil, which makes getting a visa an ordeal. It’s not entirely nasty on their part — it’s reciprocal since the U.S. puts Brazilians through corresponding annoyance.
However, there is no need to pay extra for an Australian visa. Simply go to the Australian Department of Immigration web site, where AU $20 and a credit card will take care of it. You don’t get a paper visa, rather it’s electronic. I’ve done it twice, and it worked flawlessly.