According to U.K. wedding site Bridebook , the cost of security, including snipers, undercover police and a counter-UAV system, will be about $40.1 million, or 94 percent of the total wedding budget.

But the majority of that money isn't paying for ornate flowers, classy hors d'œuvres or entertainment: It's going towards keeping the betrothed, their guests and the thousands of onlookers safe.

Meghan Markle and Prince Harry's wedding will come with a staggering bill: about $42.8 million .

If you disregard security costs, it's still a pricey affair. England-based luxury wedding planner Aimee Dunne tells CNBC Make It that expenses like food and beverage, the dress, flowers and a glass marquee for the reception will cost about $2.7 million (£2 million). That's 73 times the cost of the average wedding in the U.K.

As for who's picking up the tab, the royal family announced that it will pay for the "core aspects of the wedding," which include the "church service, the associated music, flowers, decorations and the reception afterwards."

The whopping security costs, however, are expected to be paid for largely by taxpayers. For the 2011 marriage of Prince William and the Duchess of Cambridge, the English public contributed an estimated $27 million, which allowed for thousands of extra police officers at the event.

The bride will likely be contributing, too: Markle is reportedly expected to pay for her six-figure wedding dress herself.

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