Shenzhen is served by the port of Shekou, but isn't itself a cruise port. Together, Shekou serves as the port of departure for only one sailings annually from Royal Caribbean to Vietnam and Japan.
Prices are around steady throughout the year. On average Shenzhen is somewhat expensive compared to other ports. The graph below shows the monthly average cost per day for cruises from Shenzhen (Cruises only depart from Shenzhen between December and December).