Jamie,
My wife and I pay $100 every two weeks for someone to clean our house. This is for a pretty good size house in a fairly expensive area.
It normally takes her 3 - 4 hours and consists of mopping and cleaning the bathrooms and kitchen, vacuum and dust the rest of the house and other odd chores, fold any clothes laying around, wash and remake our bed, etc.
The way we arrived at this price is she came the first time and cleaned our house and then told us the cost after that.
I agree with what someone else said, the trust factor is huge as usually neither my wife or I are home when she cleans.
