Charles was left scratching to come up with the full amount such that he had to borrow millions of pounds from his mother and which he was still paying back nearly a decade later.
As surprising as it might seem given that Charles is Lord of the Isles, Admiral of the Fleet and Grand Steward of Scotland, his personal finances are nowhere near as grand as his vast collection of titles might lead one to believe.
And that is why there was one particular moment during his son and daughter-in-law's recent Oprah interview, which, I'm guessing, might have left the royal spitting out his evening cup of Horlicks in shock.
As the cameras rolled, Oprah, Harry and Meghan gathered in the duo's chicken coop (the cleanest, most stage-managed chicken run this side of the Little House on the Prairie set) where the duchess chose that bucolic moment to reveal to the world that she and Harry had a secret wedding "ceremony" days before their official I do's.
"We called the Archbishop and we just said, 'Look, this thing, this spectacle is for the world but we want our union between us'. So, the vows that we have framed in our room are just the two of us in our backyard with the Archbishop of Canterbury," Meghan revealed as jaws simultaneously hit floors the world over.
And that was the precise moment when, I'm imagining, Horlicks ended all over Camilla's "You don't have to be mad to marry the future King but it helps" embroidered throw cushion.
Because what Meghan had just, in essence, told the world was that the tens of millions of pounds spent on the couple's lavish 2018 wedding, including a wodge of the prince's own cash, had not been necessary.
Turns out all the Sussexes wanted was the Archbishop of Canterbury to make a house call for a quickie backyard ceremony. (If only they'd had the chickens then, they could have acted as witnesses.)
What is marked is that at any other point in time, that revelation that Harry and Meghan seemingly felt their lavish public "spectacle" of a wedding was all "for the world", the British press would have nearly self-combusted in a fit of pique and 72-point headlines over such a horrifying waste of public money.
But now, as some semblance of calm has been restored, we need to take a moment to actually talk about this – because why for the love of god and Her Majesty's Treasury did the Sussexes let taxpayers and Charles spend a literal fortune on their wedding if they didn't wholeheartedly want it?
Get your abacus out, we are going to talk numbers.
See, their wedding has been estimated to have cost about $61m (£32m) according to British wedding site Bridebook, while writing in the Daily Mail, former British Minister and Privy Council member Norman Baker pegged the cost at $64m.
Of this whopping sum, the royal family is reported to have pitched in about $3.8m, a good portion of which likely came from Charles. That's backed up by a report last year when a source told the Evening Standard that the prince had "paid out a small fortune for their wedding".
(That is likely to have included the estimated $208,000 spent on flowers for St George's Chapel, $584,000 on a glass marquee for the night-time reception and the approximately $377,000 that Meghan's couture Givenchy wedding gown cost. On that front, it has also been reported elsewhere that Meghan, the only self-made millionaire to have ever married into the royal family, may have contributed towards the bespoke stunner and also to the Stella McCartney number she wore for their reception.)
However, the vast majority of the tab - an estimated 94 per cent, according to Baker's calculations - was picked up by British taxpayers, much of which went on the vast security apparatuses required for the event.
While the exact figure for this was reportedly likely lower than the $12m spent on security for William and Kate's 2011 London nuptials (we all have our 'Ten years: You crazy kids made it!' cards ready for their anniversary next month right?), the Sussex undertaking still required a serious chunk of taxpayer dosh.
Elsewhere, the UK Ministry of Defence is reported to have spent $173,000 on buying 20 new silver-plated trumpets for the event, while the local Windsor council is reported to have spent more than $1.8m on crowd control, rubbish and erecting big screens about the place.
All of which is money which could have instead gone to, say, the cash-strapped British education or healthcare systems, or to once and for all counting how many children Prime Minister Boris Johnson has. (In all honesty, the total number has never been publicly revealed. Here's hoping he himself actually knows.)
Because, if we are to take them at their Oprah-instigated word, their wedding was "for the world" - i.e. something they seemingly acquiesced to taking part in for the greater good.
In short: the cost of Harry and Meghan's wedding was just shy of the annual GDP of Tuvalu ($62m) and it all might have been a gloriously pretty waste of money.
The thing is, we "the world" didn't need them to spend a fortune on their wedding. We have Netflix now.
If the Sussexes had decided on a private or much smaller wedding, while the tabloids might have indulged in a moment of chuntering, by and large no one would have batted an eyelid. Harry has obviously never been comfortable with living in the public gaze and clearly the weight of media intrusion had played a not insignificant role in his two former serious relationships falling apart. Brits would have understood and wanted Harry to have the day he – and his bride – wanted.
All they had to do was have a hitchin' a la Princess Beatrice's last year: dig out one of Gan Gan's tiaras, have a splendid, private family day, keep Prince Andrew out of all the photos and then release a small selection of images to the world. The end.
Unlike his brother William, Harry is constitutionally irrelevant – his wedding was never going to feature a who's who of military and government whose puffed up egos were in need of stroking or foreign heads of state needing to be reminded about the pomp and majesty of the whole monarchical dog-and-pony show.
The only reason for Harry and Meghan to have a wedding on the scale and of the expense they enjoyed was because it was what they, the happy couple, dearly fancied above all else. (That and it gave them the delicious chance to ask Idris Elba to DJ the reception.)
So what conclusions are we meant to draw? That they let British taxpayers fork out vast sums of money for the lavish pantomime of a wedding for the good of the "world"?
Or, was a touch of sibling rivalry at play? Earlier this month, in those jejune days pre-Oprah, one person with "first-hand knowledge" of events around their wedding told the Telegraph: "They insisted that they had the same inflation-adjusted budget for the wedding as William and Kate – she got the choir she wanted, the dress, the carriage procession, the tiara."
Or maybe, are they a jot embarrassed they let a joyful nation open up the coffers to help them have their dream wedding, only for them to decide that life in Blighty wasn't for them?
At least they didn't do what Peter Phillips, Princess Anne's son, did to pay for his 2008 wedding and sell the photos of his big day to Hello! for an estimated $1m unbeknown to the royal family. (The move is said to have left his family "privately seething" at the time.)
When it comes time for Charlotte and Louis to wed, I have one word: elope.
British taxpayers, I would bet, are sick of paying for silver-plated trumpets.
* Daniela Elser is a royal expert and writer with more than 15 years' experience working with a number of Australia's leading media titles
