Beijing is not actually a cruise port, but is served by the port of Tianjin. In total, the cruise port of Tianjin is the point of embarkation for just twenty cruises yearly from Royal Caribbean to Asia.
On average Beijing is moderately inexpensive compared to other ports. See the graph below for the average cost per day by month (Cruises only depart from Beijing between July and October). Sailings scheduled from Beijing during the the peak season of summer are considerably more expensive than the the low season of fall.