"We don't do opulent, contrary to Hollywood's belief. It will be a wedding in the true sense," Arbiter said. "The wedding will be decorated like most brides would decorate theirs."
He added: "The church looks slightly different than what it would ordinarily look."
But this isn't just any wedding. Teams of florists have decorated Westminster Abbey to include eight 20-feet-high trees, and Buckingham Palace will have an array of flowers, for a total cost estimate of about $800,000, Eisinger said.
Also, Middleton and Prince William don't have to pay venue fees for Buckingham Palace and are not likely paying for Westminster Abbey, unlike for most weddings that take place in rented spaces, Eisinger said.
Security will be the largest expense by far, according to a fiscal watchdog, and that will be footed by the British taxpayers. But that's understandable, said Charlotte Linacre of the TaxPayers' Alliance, a grassroots campaign for better services and lower taxes in London.
Linacre said her organization is not criticizing the significant security costs, which is estimated to be about $33 million, according to the Daily Mail.
"In this kind of example, we think the police are not for the royal family but for public safety," Linacre said. "With huge crowds expected, they should be making sure people are safe."
Linacre said Buckingham Palace has responded positively to calls for the royal wedding to be sensitive to the country's relatively unstable economic state.
"We called for them to be aware to be sensitive of not being excessive with the costs when we're trying to find savings in all government departments," Linacre said, adding that the royal family is a "huge benefit" in bringing tourism to Great Britain.
Arbiter, the former palace spokesman, said security is a customary expense and cleanup might even cost less for the wedding than for demonstrations that leave property damage.
"People are generally good natured," Arbiter said. "Probably 6 to 7,000 people will line the route and leave it in a reasonable condition, unlike youngsters and anarchists."
Arbiter added that the processional route of the royal wedding will be only one mile, compared with the 2.5-mile route for the last royal wedding.
Whether the royal wedding costs are excessive, it's clear the grandeur of William and Middleton's wedding will be in contrast to Charles and Diana's, which adjusted for today's dollars, would be about $110 million, Eisinger said.
Compare that to the average U.S. wedding, according to wedding planner TheKnot:
Average U.S. wedding: $26,000
Average U.S. wedding dress cost: $1,099
Wedding cake: $540