People always forget ( Repulicans choose to ignore) that, if you do away with the Civil list. You would have to hand back to the Royal Family, all the Property/Estates, handed over to the Nation, when the Civil list was implemented.
The State gets the revenues from there now and there are a lot lot more of them, they could reclaim.
Money earned from these Estates for the Treasury, dwarf the Money given out by the State to the Royals in the Civil List.