Limits on how much parents can spend other people's resources on their kids. Which goes with civil office being a job rather than a special privilege.
However, if he didn't inherit, then his share of that money would have gone to any siblings/other relatives instead, anyway. The royal family as a whole doesn't appear to gain or lose any wealth.
Unless, I guess it's possible it could affect inheritance taxes one way or the other, if the state takes inheritance taxes?
It sounds like the inheritance is following the agreed terms of a transition away from monarchy. I don't know anything about the specific situation, but in general, I'd think that maybe a generous but peaceful separation agreement with the royal estate might work out to be cheaper (in multiple ways) for the state and the people than a harsher takeover/repossession of royal wealth would be. It really depends on the political situation.
Oh wait that’s Brave New World. Or The Naked Sun, depending on your preferred flavour of SF nightmare.
It's dishonest of you to argue that they should be treated like normal citizens while they cling desperately to their distinct and superior position. If they want to be treated as normal people all they have to do is renounce their titles.
King Albert 2 didn't want to become king but nobody else with enough capability was available. So it's not just a fun job.
But yes, the discussion to king or not pops up once in a while, and the general response seems to be we got much bigger problems.