A couple of hundred million? Five hundred? Heck, why not round the whole thing up to a cool ten figures and say it is worth a billion. After it emerged that Harry and Meghan have trade-marked the "Sussex Royal" brand, lots of experts have argued it could generate hundreds of millions in royalties and co-marketing deals.
The couple hardly need any subsidies from the British taxpayer anymore. Within a few months, they will be building a massive business empire based on their undoubted star power.
The trouble is, even in a world where celebrity is a currency, and where the likes of the Beckhams or Kardashians have managed to turn fame into wealth, the alchemy of that process is a lot trickier than it looks. In truth, the Sussexes face some major obstacles.
It is hard to know whether the name has any value once they're out of the Royal family. And it takes a lot of money-making savvy to make a success of a celebrity enterprise, which explains why as many have failed as have succeeded. Their brand is not likely to be worth nearly as much as everyone is claiming right now – and it might well crash and burn very quickly.
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If nothing else, at least "Megxit" has given us all something to argue about now that Brexit has thankfully disappeared from the front pages. It remains to be seen how quickly the royal couple can extricate themselves from their official duties and start their new life in Canada. There is no doubt, however, that they intend to use their global fame to launch themselves into a whole series of commercial ventures.
It emerged in the last few days that the couple have applied to register the "Sussex Royal" brand as a global trademark for a range of products that include clothing, stationery and, rather oddly, running "emotional support groups" (as anyone who has been watching The Crown will know, it is not really a family that does "emotion", or, come to think of it, "support" either).
There wouldn't be any point in doing that unless you were planning on setting up a series of companies based on the brand. We may soon be able to grab a cocktail at Harry's chain of bars, shop for skirts and lingerie at Meghan's, or indeed check in for some counselling, probably to resolve family arguments, at the local "Sussex clinic". And that is even before baby Archie launches his own range of romper suits. The possibilities are endless.
In fairness there is nothing crazy about the idea. Celebrity brands are a huge and growing business. Kylie Jenner managed to make herself the youngest self-made billionaire in history with her cosmetics range. In America, the likes of Martha Stewart and Oprah Winfrey have turned TV shows into huge businesses.
Donald Trump was a celebrity brand before he became president, and the Obamas managed to work the same trick the other way around.
In the United Kingdom, David and Victoria Beckham attached their image to dozens of products. The chef Jamie Oliver has branched out from television and books, and so has Gordon Ramsey, while Katie Price has launched endless stuff even if no one can quite remember what she was famous for in the first place. In a small way, the Royal family have already dipped their toe in the waters with Prince Charles's Duchy Organic food range.
If it is done right, it can be an incredibly powerful set-up. The celebrity brings fame, aspiration, and a ton of free publicity, and if they can match that up with a well-designed product, great distribution, and wrap it all up in a value-for-money package, then a star brand can be a lucrative proposition.
It is growing all the time as well. In a world where traditional advertising has less and less traction, and fame obsessed social media is often the only way to cut through to a mass market, celebrity is more important than it has ever been. Plenty of consumer markets can be taken over by someone with the right kind of reputation.
But Harry and Meghan? Just because you are famous, it doesn't automatically mean you can turn that into ringing cash tills. In truth, the couple face three big challenges.
First, it is not clear whether the brand has any real value once the couple are outside the Royal family. True, Meghan was a moderately well-known actress, but Harry is only famous because of his parents, and brother. Once he steps outside of that, he may find his star power starts to fade alarming quickly.
Other celebrities have made themselves famous from nothing, and know how to keep themselves in the public eye, but there is no evidence the Sussexes have that kind of ability.
Next, they will need to some serious business savvy behind then. There is no point in just slapping a famous name on to a rubbish product. It needs to be well-designed, well-made, competitively priced, and brilliantly distributed. All that is a lot harder than it looks.
Finally, brands sometimes generate sales, but that is not the same thing as profits. Victoria Beckham has made big losses on her fashion line and Jamie Oliver's chain of restaurants crashed spectacularly. Get anything wrong, and you are punished.
It is easy to bandy around big numbers. And celebrity brands can sometimes be money-spinners. But there is a lot more to pulling off that trick than simply generating lots of column inches, and chalking up millions of followers on Instagram and Twitter.
The stars that make it work are commercially savvy first, and famous second, not the other way around. In truth, there is no evidence Harry and Meghan know how to make that work – and it is going to be a long, long time, if ever, before they are on the Forbes billionaires list, or floating their company on the stock market. They might even have to return to working for the Royal family.