When Charles became prince he was given the Ducyhy of Cornwall. Now that he is king, his son gets it, just so that each has an income. That duchy that William receives is now worth $1. billion. Have a read of Jared A Brock. He writes here on Medium. It's pretty sickening.

Tere is so much we don't know and will never know about the family

https://www.google.com/search?client=firefox-b-d&q=the+duchy+of+cornwall+to+prince+charles