Jetstar and tiger have flights for $ 46.
Not too bad
Keep in mind that Tiger is no frills, think of Spirit.
Quite common for delays, and there is only a flight every couple of hours so it is not like you could get reseated on another flight shortly afterwards. Unlike Virgin or Qantas which have flights every half-hour or hour.
And Tiger love charging you for every stupid thing.
Also, if you dare come even one second after check-in closes 45 minutes prior to departure, they will not let you on that flight. Instead, they will bump you to a flight several hours later, and charge you for it too. Even if you already checked in online.
I once got stuck in traffic on the way to the airport, and arrived late. I told the staff that my flight was imminent, but they told me I have to get on line and hope for the best. So, I get on line, with two people ahead of me, and half a minute later they announced that check in has closed for my flight, being that it was precisely 45 minutes before the flight. When I got to the desk, the agent told me she cannot check me in to the flight, even though she knew good and well that I had been waiting on line. She offered me the lowest fare on the next flight a couple of hours later. However, I didn't have the time to wait, so I ended up buying a last minute ticket with Virgin, who obviously had no problem selling me a ticket for a flight less than 20 minutes later.
In summary, don't use Tiger unless you have lots of time to spare in case of delays, fully understand all the extra charges for baggage etc, are NOT travelling with family, or there is any chance that you might be even slightly delayed getting to the airport.
They call it "Terrible Tiger" for a reason.