Officially the upkeep of the royal family to the British taxpayer is about £40m .
However, when all the hidden expenditure is included the actual figure might be as ten times higher.
Hidden expenditures such as security for the royal family, renovation and upkeep of royal buildings, and also the income from the Duchy of Lancaster and the Duchy of Cornwall – despite belonging to the nation - goes directly to the Queen and Prince Charles respectively, depriving the treasury of tens of millions of pounds every year.
When all this hidden expenditure is included, the real cost of the monarchy to British taxpayers is likely to be around £334m annually. (almost half a billion dollars) annually.
How is this tolerated in times of austerity, when the British government is cutting back on disabled and old peoples benefits, is beyond me.
Source : https://republic.org.uk/what-we-want/royal-finances