I've answered you before but you ignore the fact that the Crown Estate profits go to the Treasury, and then the Sovereign Purse is paid out.
The public pay for security which is pence.

Deal with 27 separate countries? What a waste of time and effort when we can trade with one power? I remember her promises to NI, which were rubbish. Johnson couldn't sort it out and Sunak has had to compromise.

So are many rich people. As for the royals income, most of it comes from the Crown Estates via the Treasury.
Taxpayers pay for security, which would apply to a President.