But the heir to the throne may struggle to foot the growing bill if Prince William, Kate, and Prince Harry end up taking on much more royal work as the Queen and Prince Philip slow down.
Charles's principal private secretary William Nye conceded that his boss would have to look carefully at how much he could continue to fund the activities of the three younger royals in addition to his and Camilla's duties if the balance of work changed.
That may come to a head if William decides in September to quit his job as an RAF search and rescue helicopter pilot and become a fulltime working royal. "Whatever the Duke of Cambridge's plans, the Prince of Wales would have to look carefully at how he continues to fund the official activities of the staff and support for the five senior members of the Royal Family whom he is paying for," said Mr Nye.