I've no idea about the true costs and benefits, I doubt if anyone has tbh.
However, if they bring in such huge amounts of money why do we all have to pay for them at all. It's interesting how support for the Royal Family fluctuates depending on what they're up to. I'd imagine there are people who were sure the Queen, and her family, were involved in Diana's 'accident' who are now grieving over her passing.
I'm not fussed about the Royals, either way, it's just another soap opera imo and pretty harmless.