"They have already milked far more than their worth from the coffers of Great Britain and the Commonwealth, IMO."

You don't know how the monarchy is financed, do you?

Look, there are a number of estates which belong to the Crown - not to the Monarch. These estates generate revenue - income. That income is collected by the Government and a certain percentage, around 25%, is allocated to the monarch in the form of the Sovereign Grant, to be used for official activities and admin. The rest goes to the Treasury as part of government income. So you and I, as taxpayers, pay exactly zip toward the monarchy.