I understand the tax burden argument and have no idea if the following is true, but I’d imagine that every penny spent is earned back multiple times over in tourist/media revenue. Not to mention the vast sums raised for charity by the royal family. If nothing else, they serve as a living Tussauds type cash cow.
I’m hardly pro Royal, but I think calling for their heads is a little far fetched.
Regardless of treatment, the old bird is doing incredibly well for 90.