STLcruiser

Does anyone know the price of the transport to port from any of the three Baltimore/DC area airports? I know taxi from BWI is reasonable, but I am combining the cruise with a visit with relatives that live in Virginia. They might be able to transport me to/from DCA or IAD, but not BWI. Alternatively, if I rent a car one way to Baltimore, is there a rental car that provides a shuttle to/from the port? Thanks!