heh the northern suburbs is a bit shocking with the cost of rent averaging $350 - $420 per week for a 1 bedroom apartment. About $300 for a studio apartment. Prices start at $480 for a 2 bedroom place. These are Chatswood central prices so places get cheaper if they radiate into the smaller suburbs away from amenities. They get more expensive though if its got a view (North Sydney for example), and they get more expensive again if its one of the prestige suburbs (there's a lot of wanky suburbs north of the bridge).
You can find cheaper if you are willing to share accomodation or move into a less than perfect place you can get away with as low as $260 - $280 p/w. You may not find suitable parking at those cheaper locations though.