If its the driving that bothers you, another option is to catch the bus down each morning/home each night. Leaves from Fed Square and drops you back there each night. Buses are actually coaches, so pretty cushy and all have toilets/tvs. I found it to be a really awesome option last year, since I live in Melbourne and couldn't justify staying out at the Island and meeting their "3 night minimum" and paying through the nose for it. Might give you a few more options to find something cheaper in the CBD. From memory it was about $35 return each day, booked through Foxtix.