Depends on what happens with the aristocracy and landed gentry in general, I’m sure they would still be wealthy but may have to generate money via other methods.
France does absolutely fine for grandeur and symbolism, without an unelected family and their hangers on.
From a quick look the total estates took in ~£50,000,000 in 19/20 prior to covid. Where all that money ends up (does all/some of it actually benefit normal people) is another question. Those estates would still take money in if they weren’t royal, in fact their purposes could be diversified to generate more revenue potentially.
Also, Elon Musk isn’t an unelected, hereditary head of state with everything that comes with that role.
People can support the monarchy all they want, most of my family are of the monarchist persuasion, I don’t agree with them there but don’t feel too strongly about it until it’s put forward that they’re some kind of essential, benevolent or benign presence that upholds all goodness in this country. Just like I don’t need religion to show me what a decent person looks like, I don’t need royalty to provide a beacon of morality either. If others need that, well, that’s their thing.