The Queen's funeral and the King's coronation are expected (I'd take these estimates with a pinch of salt, but still, it's going to cost a LOT of money) to cost £6billion to the UK economy. That doesn't cover the costs of changing titles, currencies, signage, uniforms, portraits etc etc. This will cost us billions, all while are going through a major cost of living crisis and are on the brink of recession.
The royal family didn't start paying taxes on their private finances until the 90s. The civil lists were only made public in the 1970s. The queen herself inherited an estate worth £121 million in today's money. The queen alone had a personal fortune of £275 million to £340 million. All of this privelege, just by virtue of birth.