To land a high-profile ambassadorship, it helps to have raised a ton of money for a successful presidential candidate and know how to throw a good party. That’s one reason why President Obama is considering Vogue editor-in-chief Anna Wintour as the next U.S. ambassador to the Court of St. James’s in the U.K. Wintour raised more than $500,000 for Obama and inspired the “Runway to Win” fashion line that brought in upwards of $40 million for his campaign.

But that’s just the price of admission. The funds embassies receive from the U.S. Department of State don’t begin to cover the high costs of the frequent parties and dinners ambassadors are expected to host. Some wind up paying more than $1 million a year out of their own pockets, according to one of the president’s top donors who requested anonymity because he didn’t want to discuss private conversations.

This is why the high-profile postings to places like France and Italy typically go to wealthy donors, rather than career diplomats. The current ambassador to the U.K., Louis Susman, a former Chicago investment banker, holds three to four social events a week, says an embassy spokeswoman, who declined to give a cost estimate for these soirees. “Political ambassadors have more resources and are able to entertain a little bit more lavishly,” says Mel Sembler, a Florida Republican fundraiser and former ambassador to Australia under George H.W. Bush and to Italy under George W. Bush. “We did spend more than our budget, because that’s the way we entertain.”

Winfield House, with art by Ellsworth Kelly and Mark Rothko, sits on 12.5 acres in LondonPhotograph by Elizabeth Gill LuiWinfield House, with art by Ellsworth Kelly and Mark Rothko, sits on 12.5 acres in London

In exchange, appointees get perks—beginning with the sought-after title of “ambassador.” In some Western European countries, they live in sprawling estates such as London’s Winfield House. Its 12-and-a-half acres of private gardens are exceeded only by those of Buckingham Palace. The ambassador to Italy can avail himself of a three-story, 5,000-bottle wine cellar at the Villa Taverna in Rome. American and Italian vintners and wine enthusiasts funded the $1.1 million cellar—accessible via catacombs—in hopes of encouraging conviviality and commerce between their countries. And through the State Department’s art-in-embassies program, ambassadors can surround themselves with the finest works of art belonging to U.S. museums.

The American Foreign Service Association reports that about 31 percent of ambassadorships are held by political appointees, the rest by career foreign-service officers. The appointees typically request the richest countries. “If you have a choice between France or Botswana, it’s no choice,” says Tex Harris, the association’s former president. Over the years, efforts have been made to offset the costs of living at the pricier embassies so that a broader variety of people can serve there. After his tour as ambassador to the Court of St. James’s in the Nixon administration, Walter Annenberg established a fund to help pay for the upkeep of the diplomatic mansion. “Just filling the flower vases for the embassy in London is very expensive,” Harris notes.

Mark Rothko, Photo courtesy of Heath Cooper and Paul Bricknell, Senior Photographers, Sotheby’sMark Rothko, “Orange and Tan,” 1954

Congress is unlikely to increase embassy social budgets. Spending taxpayer dollars on garden parties has “always been a sore point for people who misunderstand that this is work, it’s not play,” says Susan Johnson, AFSA’s current president.

Wintour’s competition for the U.K. posting includes Obama’s national finance chair, Matthew Barzun, who married into a Kentucky bourbon fortune. Wintour is also said to be eyeing Paris. She’d have to square off with hedge funder Marc Lasry, the founder of Avenue Capital Group who raised north of $200,000 for the president this year. Former Arizona Representative Jim Kolbe, who oversaw State Department funding while on the House Appropriations Committee, likens the competition among the wealthy for choice ambassadorships to the fondness some billionaires have for playing astronaut. “It’s like paying $25 million to go into space,” Kolbe says. “It’s a fun thing to do.”

The bottom line: Wealthy donors—who can afford to spend their own money entertaining on the U.S.’s behalf—hold 31 percent of ambassadorships.