What would it cost to purchase in a store the kind of wardrobe Nancy Reagan has ordered to wear in the celebration of her husband's second inauguration?

Certainly more than $25,000.

"That's ridiculous," Mrs. Reagan told a wire service reporter of that estimate.

In fact, the actual price paid by Mrs. Reagan is a private matter, adjusted by the designers because of the exposure given their designs when she wears them. And since Mrs. Reagan's purchases are rarely made through stores but rather directly from the designers, it is possible that she is unaware of the retail price.

However, a survey of industry sources confirms that the costs, at retail, for the clothes Mrs. Reagan plans to wear to the major inaugural festivities, excluding some accessories, would be $46,000.

The White House has declined to comment on the figures.

But according to retailers and manufacturers, the costs break down as follows:

* A totally beaded gown with Art Deco design and bolero effect by James Galanos, $22,500. The Austrian and Czechoslovakian glass beads, took more than 300 hours to apply by hand, the designer said last week.

* An electric blue matching coat and dress, each with a chain link belt, by Adolfo, $2,800. The designer has also made a roller-brimmed hat in the same blue to wear with the costume. (The designer is lending Mrs. Reagan link earrings and necklace to wear as well.)

* A lacquer-red, heavy silk side-draped gown by Bill Blass to be worn to the gala, $3,000. The gown is similar to a dress Blass is offering his customers for spring.

* In addition, Mrs. Reagan has also ordered a white double-faced wool coat with three jeweled buttons that close off to the side to wear over the white gown, $6,000; and a white mink blouson jacket, also a Galanos design, $10,500.

* A red wool jersey wrap, made especially to go over the red dress worn to the gala, $1,000.

* A twisted pearl chocker and earrings by Kenneth Jay Lane to wear with the red dress $200. (Actually, the designer made two necklaces to give Mrs. Reagan a choice.)

This $46,000 total does not include specially handmade shoes or other acessories to complete each outfit. No doubt Mrs. Reagan will wear some of her favorite dresses and accessories to the parties connected with the inaugural.