I`m not sure about reasonably priced but I know the Westin St Francis and the Parc 55. I would think Parc 55 is the cheaper of the two. Try to aim fairly near Union Square if you can because you`re central for things. Be careful of anywhere south of Market St, as you can turn corner and be in a whole other world (of drop outs and drunks). You could save money on Room Only deals if you stay central as there are loads of places to eat.
I stayed at the Holiday Inn at the waterfront, or whatever that part of town is called. Very convenient for boat trips to Alcatraz and seeing the sea lions on the jetties. You know when American hoteliers politely ask "Did you enjoy your stay?", I pointed out (truthfully) there was a generator buzzing under the floor, so the manager gave me a refund!