The dock spares the PB's micro-usb port from excessive wear. I paid $13.50 for mine on clearance at Staples---not sure if there any Staples in Canada.
That said, I'm glad that's all I paid---as my dock does not mate properly with my PB about half the time. I always have to use the Battery Guru app whenever I charge with the dock, as only BG ensures that I am actually charging---the lightning bolt symbol often lies.