It shouldn’t matter what your actual worth is in terms of your rank in line to the throne. If you are the son of the reigning monarch and brother of the future monarch, you should have certain provisions made for you so that you can live with some dignity and you are not treated like a distant cousin. You are closer in a familial sense than your rank indicates.
I can’t know for sure, but before the falling out happened, I think the essence of the problem was that Harry felt shunned by his father and brother. Harry obviously anticipated an additional title and/or some sort of Manor House when he was married as that is generally when those things are bestowed.
Harry didn’t have a Coronation coming up; his marriage was his one and only “big event” and change in status. He was very good at his charity work after all and anticipated doing that as his full time job when he left the army.
If you think about it, the Queen gave Anne Gatcombe Park, Andrew ended up with the Royal Lodge and Edward has Bagshott Park.
It was probably a bit of a bitter pill for Harry to swallow to have to show his new wife Frogmore cottage with 10 bedrooms, when his uncle Edward is living in Bagshott which has 120 bedrooms and is worth 45 million and with Andrew down the road in a 30 bedroom pile worth £30 million!
Most of us would be very pleased with a ten bedroom house but in a world where favours and titles are bestowed on you by your parents, and you don’t (at that point anyway) have the ability to earn your own income, I can imagine that these things really matter. Also, Harry didn’t have a mother to stand up for him remember.
Is it possible that Charles decided to show the world that he was “slimming down” the monarchy by putting Harry and Meghan in one of the smallest house on the Windsor estate and detract from the fact that he owns or has access to twelve properties himself, many of which are palatial with substantial lands attached? And he hasn’t as yet slimmed down his own property portfolio at all?
Edited to add: so when you say Harry is deluded and has an inflated sense of his own importance; I don’t think that’s quite right given he is the son of the current monarch and brother of the future king. He should at least have been given a home and status on a par with that and not treated like a distant cousin.