Monaco has a small selection of hotels with many of them being in the uber-luxurious category. One or two budget options do exist, but you may need to nip over the border to France to find something which offers better value for money.
Victoria Hotel, Roquebrune-Cap-Martin
Victoria hotel is located right on the beach in Roquebrune Cap Ferat near Menton town centre with easy access by bus from Nice airport. It is very well located if you want to visit places like Monaco, Nice, Cannes.