After Ana Pettus, a 42-year-old mother who lives in Dallas, watched a gold minidress with a plunging, fringed V-neck go down the runway at the Balmain show in Paris last year, she knew she had to have it.

She bought the piece—she wears it as a tunic instead of a dress—along with three others from the fall 2010 collection at the Paris boutique of the luxury French fashion house. Price tag: €55,150, or about $74,000.

The...