Depending on what you are looking for
A two star hotel room with 2 beds within walking distance from Moscone West costs 80 bucks according to Expedia
Of course if you're looking for a four star, then cost isn't a concern in the first place
I believe there is a Marriott and a Clarion which are nice near the airport. Probably less expensive and you could BART it into town. Get off at Powell or New Montgomey.