When Prince Harry and Meghan Markle marry at Windsor Castle on 19th May, we're expecting all the fanfare  and fabulousness befitting a prince and a (hit) show girl. And it's no surprise that the wedding of the year will come with a suitably ritzy price tag - one that would send most 'civilian' brides running for a stiff glass of Prosecco.

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In fact, experts estimate that the total cost of the celebrations will be a cool £21 million - roughly a thousand times more than the average UK wedding (if Prince Charles is reading this, we hope he's sitting down with a cup of Earl Grey - it's been announced that the royal family will be footing the bill). 

So the million dollar (or 21-million-pound) question is: what exactly will they be spending it on? 

Sources close to the couple have hinted that Meghan Markle's wedding dress will come in at a couture-worthy £400,000 - and whilst it's tempting to file this envy-inducing spending spree under 'perks of marrying a prince', it's worth noting that Kate Middleton and her family paid for her wedding dress (although the Sarah Burton for Alexander McQueen number cost a comparatively modest £300,000!), and it's likely that Meghan will do the same. 

Speaking of the Duke and Duchess of Cambridge, their 2011 nuptials make a useful litmus test for sussing out the costs involved in pulling off a wedding that packs a punch in terms of size (there's no devil-may-care slashing of the guest list when global relations rely on you inviting dignitaries from every corner of the globe), sophistication - the world is watching, after all - and security (policing costs were between £7 million and £20 million, according to Express.co.uk).

And with Kate and William's two cakes reportedly totalling over £50,000, and a flower bill of £14,000, it's easy to see how costs can mount when you're keeping up with the Armstrong-Joneses and every aspect of your day has to be literally fit for a queen.

Then, of course, there's the honeymoon. We know that Meghan and Harry are partial to a luxury safari, but forget the Big Five - when it comes to their romantic getaway, sources say it's more like whopping 120k; Meghan's gift to Harry, apparently (note to grooms: don't get any ideas).

So what's in this for us regular, non-regal brides-to-be with regular, non-regal bank balances? Well, as we set about planning our day and creating our princess moment, isn't it nice to buy into the fantasy (no pun intended), pore over the details of a day that showcases the very best suppliers and the chicest ideas, and soak up the magic of a real-life fairytale? And that's why, when it comes to bridal inspiration, a royal wedding is priceless.