The vexed issue of royal finances......
Back in the mists of time, the Norman Conquest decreed that the Crown owned everything: but grants of land and other sources of revenue were made to assorted underlings on the understanding that the power and wealth they got from it required a duty of service, loyalty and the supply of warriors and wealth to the monarch as and when required. The point of Domesday Book was as much to show the rich and mighty just how much benefit they had from the Crown as vice versa. Over time, these benefits came to be seen as rights (predominantly of the rich and powerful interests like the barons, the Church and the merchant guilds of the City of London), though that didn't stop the rich and powerful being as exacting over their underlings - and Magna Carta and its associated charters recognised those rights (of the rich and powerful) and the primacy of those rights and the rule of law over the monarch. Also over time, it came to be accepted that the Crown was not only bound by law but needed parliamentary approval for extra taxes; Charles I's attempts to undo all that led to the Civil Wars of the 17th century and the final establishment of parliamentary sovereignty. By the 18th century, the separation of the finances of Crown (as government) and the royal family (both personal and for state ceremonial and the like) became greater, culminating in the settlement of George III that the government Treasury should receive the income from the Crown Estates rather than the Royal Household, but in return Parliament would grant the "Civil List" payment for the state and personal expenses of the monarch and royal family from the totality of general government income. Over time, this money has been tied to support for the public functions of the institution, rather than a personal salary (and to confuse the issue, the royal family and individual royals have separately been able to build up inherited private estates and income for their personal business). But about 10-15 years ago, it was decided that the Civil List would be replaced by a percentage of the Crown Estates income, so it all depends on whether you think the inherited rights and incomes from the Crown Estates count as belonging to the taxpayers, the Crown (as the government) or the Crown (as the monarch and family).
There are also grey areas about the use for supposedly state business of various services run on other government budgets, such as RAF transport and so on, and debate about maintenance of assorted Crown (rather than family) residences, and exactly how many assorted office and household staff it takes to keep the state visits, garden parties, openings and unveilings going, and all the associated paperwork. But there are annual reports about what is spent on what, for those who want to delve into it.