"Buck House is mainly an administrative building for the head of state, with offices and function rooms."

Absolutely not the case. Do read the wiki article on Buckingham Palace. You'll be amazed at what goes on there on top of the "administrative" side of things (which could easily be executed in ordinary offices anywhere in the country, by the way). And we pay for it, including the hundreds of millions needed to renovate it. As for the Crown Estate, and those huge "duchies" that Charlie owns, they simply should not exist beyond full nationalised control, and the filthy-rich monarch should not be able to hive off tens or hundreds of millions per annum from them for purposes that are generally hidden from public view and which are dubious at best.

Finally, are you able to tell us what happens to the fifty million that the "royal residences"(gosh, don't they need so many of them! Still, I don't suppose there are too many grouse to shoot at round Buckingham Palace) earned last year?