I do not mean the 50watts that the charger has is decreased by the charger's inefficiency. Its is the input power to the charger that has to account for the inefficiency.

To get 50watts out of the charger, you power supply is supplying somewhere 60 to 63 or maybe more watts to make that 50watt output possible. If you had a 50watt power supply, you wouldn't be able to run the charger at its full 50watts.