The cost of the coronation of King Charles III in 2023 is around 200 million euros. It is less than a single day of the French "whatever it costs", whose total cost was 80 billion.
For comparison, the 2021 Tokyo Olympics cost €12 billion, 60 times more than this coronation. The paradox on which the British political system is based is that it is not based on the cost of a coronation, but on the prestige of the British Crown in the world. The price is not exorbitant.