Beijing is not itself a cruise port, but is served by the port of Tianjin. Combined, the cruise port of Tianjin acts as the point of embarkation for just one sailings yearly from Royal Caribbean to Asia.
On average cruises from Beijing are somewhat expensive compared to other ports. Check the graph below for the average cost per day by month (Cruises only depart from Beijing between April and April). Prices are about steady throughout the year.