From choosing the cake to the flowers and even the chair-covers, anyone who's ever planned a wedding knows it can be eye-wateringly expensive.
But when it comes to royal weddings - with all the VIPs, security and extra extravagance - the bill runs into millions.
So what do we know about the expected cost of Prince Harry and Meghan Markle's wedding, and how much will the taxpayer be paying towards it?
The wedding will be held in Windsor. And crowds in excess of 100,000 people are expected to descend on the town.
Invitations have been sent to 600 guests, with a further 200 invited to the couple's evening reception
On top of that, 1,200 members of the public will attend the grounds of Windsor Castle.
Managing these sorts of numbers requires substantial planning.
And security will almost certainly be the biggest single cost.
The Home Office wouldn't comment when Reality Check contacted it, saying revealing policing costs could compromise "national security".
Likewise, when we rang Thames Valley Police, it said: "We aren't going to give you any data I'm afraid - even though we know you love numbers."
However, we do know £6.35m was spent by the Metropolitan Police (ie the taxpayer) on security for Duke and Duchess of Cambridge's wedding.
That's based on a Freedom of Information request released to the Press Association.
But it's difficult to draw a direct comparison with Prince Harry and Ms Markle's wedding - the location and guest numbers are different.
Kensington Palace hasn't released any details of what it plans to spend on the wedding.
That's not really a surprise given that the official cost of Prince William and Catherine's wedding has never been revealed.
That leaves us with unofficial estimates and as such they need to be treated with some caution.
Bridebook.co.uk, a wedding planning service, says the total cost of the wedding could be £32m - including the cost of security.
It put the cost of the cake at £50,000, the florist at £110,000, the catering at £286,000, and so on and so on.
Reality Check contacted the company's owner, Hamish Shephard, to ask about the methodology used to arrive at the estimate.
He said the £32m figure had been based on the assumption that the Royal Family had paid for everything at market rate.
But in the absence of any official data, this is still guesswork - however well informed.
For example, we don't know if suppliers would offer a substantial discount for the privilege of providing their services for a royal wedding.
The cost of security for the wedding will be met by the taxpayer.
Initially, Thames Valley Police will have to absorb the cost itself.
But the force will be eligible to apply for special grant funding from the Home Office after the event in order to claim back some of the costs.
Special grant funding is a separate pool of money forces can apply for if they have to police events outside their usual remit.
As for the rest of the total, the Royal Family has said it will be paying for the private elements of the wedding.
Every year the Royal Family gets a chunk of money from the annual Sovereign Grant, paid directly by the Treasury.
The grant is calculated on a percentage of the profits from the Crown Estate portfolio, which includes much of London's West End.
This year it's worth £82m.
Some members of the Royal Family benefit from additional income.
For example, Prince Charles gets money from the Duchy of Cornwall estate, a portfolio of land, property and financial investments.
But it's not clear which "pots" the palace will choose to fund the wedding from.