"Now I can understand why clothes are so expensive," commented Marilyn Funderburk, former deputy White House social secretary. For close to a half-hour she watched Dutch-born fashion designer Koos Van Den Akker place, turn, pin, unpin, cut and re-pin a piece of silk print on black fabric. He was, in fact, making a collage design for a coat in a setting meant to recreate his Madison Avenue atelier, set up for the evening in the Lunn Gallery.

It was a benefit for the Washington Project for the Arts, a center for visual and performing arts in downtown Washington, and an appropriate one. While the designer was "performing," there was much that was visual to the more than 200 who paid $45 each for the evening: not only the Yousuf Karsh photographs where Van Den Akker was working, but the Martin Silverman sculptures next door in the Diane Brown gallery, and the Van Den Akker clothes displayed for close inspection on mannequins in those and several other galleries.

"No one else does this one-of-a-kind work," actress Mariel Hemingway explained to former vice president Walter Mondale as they approached the work table of the fashion designer. Joan Mondale had stopped by the exhibit earlier en route to another party and returned with her husband.

Van Den Akker showed the Mondales how he mixed new and old fabrics, synthetic and naturals in one coat. "You do it all yourself?" questioned Hemingway, who was wearing a Van Den Akker tunic over trousers she had borrowed from her hostess Val Cook, vice president of Saks-Jandel, sponsor of the show. The designer makes the couture, one-of-a-kind pieces himself; others he creates and then they are made up by 85 expert sewers in his factory, he explained.

Van Den Akker, who had traded in his permed hair, sport jacket and tie look of a year ago for a pony tail, printed suede pants, lizard boots and loose sweater, continued to work against a backdrop of fabric bolts, sketches and fabric swatches as models selected clothes from a rolling rack to change into on the balcony over the gallery. A sewing machine was ready for his use.

Guests moved among the several galleries, where traditional Dutch food was offered by Barens Specialty Foods in Alexandria. There was a varied cheese market in front of the John Van Alstine works at the Osuna Gallery, desserts with the American decorative arts at the Newcomer/Westreich gallery, delicatessen specialties in front of Pete Omior paintings in the McIntosh/Drysdale gallery, sate' with peanut sauce in the Kornblatt Gallery, truffle pate' at Diana Brown's, and pea soup (snert) and meat balls (gehakt), those two being favorites of the designer, just behind where he was working. Dutch beer was everywhere.

Even at age 4, Van Den Akker was making dresses in crepe paper with patchwork designs. After working as an unpaid assistant for three years at Christian Dior in Paris, he came to New York in 1968, perched himself by the fountain at Lincoln Center and peddled his clothes, saying, "I'm from Holland. I need some women to dress. Would you let me make you a dress?" Then his clothes cost around $30. Today his suits start at $400, and he makes as many as 400 of some designs. "When you consider the whole country, that is not so many people having the same thing," he said. Elizabeth Taylor, Ellen Burstyn and Joan Kennedy are among those who own his things.

Robin Hill, a painter of birds, stood alongside the table, watching the designer work over the placement of an uneven piece of tweed wool until he finally tossed it aside. Hill, like a sidelines coach, appeared relieved. "There is no difference between a collage in fashion or a life study. They are both the work of artists," he said.