With regard to the Sovereign Grant, I would like to correct what I think is some misinformation being talked about. For clarity, I want to say that I am not doing this because I am all in favour of royalty or totally against it. It's the system we have at the moment.
Now, down to business:
The Crown Estate is owned by the Monarch, but in 1760, George III surrendered the management of this part of his holdings to Parliament in return for a fixed annual payment, which became the Civil List. Effectively, that means that the profits go directly to HM Treasury to fund Government expenditure. (There is plenty more information online.)
The Sovereign Grant was established in 2011 by the Sovereign Grant Act. This abolished the Civil List and introduced a single payment to the Monarch to fund Royal Expenditure. Payments to staff, reimbursement of expenses incurred during official duties (by all the working Royals) and upkeep of Palaces owned by the public (Buckingham Palace, Windsor Castle etc) are funded by the Sovereign Grant.
According to the latest figures, the Crown Estate generated a profit of £1.1 billion in 2024, which was paid to HM Treasury. The Sovereign Grant was paid at 12% of this profit - quite a sum. However, none of this money is paid through the taxes raised by HMRC.
As I said, all this information is readily available online, for anyone who wants to know more. As I openly acknowledge that I am a pedant, I'm writing this to counter the idea that 'they' are living in luxury while 'our money' is paying for it. Both The King and The Prince of Wales are fabulously wealthy and perfectly able to manage on the profits (maybe salaries) that they take from their private Duchies - which were established in 1399 (Lancaster) and 1337 (Cornwall) to provide private incomes for the Sovereign and Heir - on which it is understood that they pay tax, but (I think) scrapping the Monarchy and installing a President is still leaving the Royal family with its wealth intact (and possibly the return of the Crown Estate), leaving us to fund the total cost of a President. Personally, I'm not sure it is worth it at the moment, but I'm not prepared to argue for it.
Anyway, I hope this helps set the record straight about funding the King.