mikamika - where are you from?
Would you prefer to stay somewhere with access to lots of restaurants?
Are you saying that West Ryde is expensive - or have you been looking at some seriously expensive northern suburbs.?
Personally - I don't like West Ryde; I worked there for a number of years.
Seven Hills is a fair way out - may be cheaper, but probably not too good if you are single and looking for company. It's pretty much a families area.
Depending on the sort of accommodation you want, perhaps consider Burwood/Strathfield / Homebush - good access to the city, plenty of apartments, restaurants, people, sporting clubs, churches. Next - perhaps Parramatta - not as buzzy, but plenty of apartments and restaurants.
It all depends, really, on just what you want. I'm no clearer about that. House, apartment, share house.? Need parks? I have no idea what you consider a reasonable price.