Wearing donated gowns represents a change in practice from the Bush administration.
Anita McBride, chief of staff to Laura Bush during her time as first lady, said Mrs. Bush paid for all her clothes, including her two inaugural gowns: a red crystal-embroidered gown by Texan Michael Faircloth and a silver and blue V-neck creation of Oscar de la Renta.
McBride credits the Obama White House with finding a cost-saving way to "keep Mrs. Obama in all those incredible clothes and to have the use of them not once but multiple times."
The costs of a custom couture gown can be phenomenal, particularly if it is highly embellished with something like beading.
New Yorker Sarah Phillips, who designed Hillary Rodham Clinton's 1993 inaugural gown, puts the full cost of that violet beaded lace sheath in the range of $50,000, with the Presidential Inaugural Committee paying $10,000 and Phillips and the workshop covering the bulk of the costs. Phillips isn't sure whether Clinton herself paid anything toward the dress, but the Smithsonian's website describes the gown as a "gift of Hillary Rodham Clinton and the Presidential Inaugural Committee."
Lawyers who served in the Obama and Bush White Houses describe taking care in working with the first lady's office to ensure that arrangements with designers didn't run afoul of ethics rules designed to guard against conflicts of interest and questionable quid pro quos.
Beyond the unknowns about how often Mrs. Obama's clothes are donated, there are questions about how much she pays for those she purchases.
In a 2011 Washington Post story about Mrs. Obama's personal assistant, Meredith Koop, the first lady's office said Koop acted on Mrs. Obama's behalf "in arranging for purchases, including considering the best offered price and buying on discount if discounts are available."
That's still true today, the first lady's office says, without elaborating.
Several designers who have provided clothes for the first lady declined to discuss their arrangements. But given the prestige that comes with dressing Mrs. Obama, it's widely thought that designers are eager to cut the first lady a break. Former White House lawyers said any discounts provided to the first lady would have to be in line with what designers offer other top customers to avoid being considered gifts.
Paco Underhill, author of "What Women Want: The Science of Female Shopping," said the markups on designer clothes are "astronomical" — and the discounts can be steep as well.
"Some of the routine discounts that people ask for are 40 percent off," he said. "Whether they get it is subject to somebody's discretion."
First ladies have tried all sorts of tactics to hold down their clothing costs, including keeping some dresses in rotation.
Mrs. Obama wore the same dress to this year's Mother's Day tea that she'd worn to lunch with Katy Perry in October 2012. She often switches around separates, belts and other accessories to give clothes in her wardrobe a fresh look.
Recycling carries its own risks.
Mrs. Bush, in her memoir, tells of arriving at a TV studio and noticing a picture on the wall that showed she'd worn the same suit to her last interview there.
"Quickly, I exchanged tops with my press secretary, so that it would seem as if I had more wardrobe variety," she recalled.
Associated Press writers Brett Zongker in Washington and Beth Harpaz in New York and news researcher Rhonda Shafner in New York contributed to this report.
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