This all started because we were discussing how they are going to manage financially in the future
I would say, they're not managing.
They are absolutely hemorrhaging money - many, many millions a year - and the sources of income have dried up now.
It's how a lot of 'Hollywood celebs' go bankrupt, or die owing $500 million dollars. Outgoings for lifestyle, staff, security, entourage, expense accounts, houses & property, 1st class travel, etc far outstrip incomings.
Harry is thick but venal. He's probably already threatened Pa with 'being reduced to Uncle Andrew's way of life' if he's not sufficiently bankrolled - but where does it all stop? $10 million a year? $30 million? More? Many mild-mannered republicans like me hold the view that the monarch's 'private money' has public origins i.e. it once belonged to others, and requires public oversight.