the royal family costs the UK tax payer ~100m a year[0], which is about the cost of the three nuclear bombs in the US or less than one of the ill-advised F-32 purchases Australia is making. it's also maybe a 1/10th of the amount of money stolen by Tory mates for their various PPE crimes during the early pandemic.
every country has very very dumb shit they piss money up the wall over, but it's not a game changing amount of money.
0: dodgy source: https://www.standard.co.uk/news/uk/how-much-royal-family-cos...