Costa emphasized trouser suits in the spring 2004 collections. Costa also paired clingy, translucent daytime skirts with cashmere tops and layered
cardigan over rumpled white shirts and men's ribbed undershirts with loose cotton shorts. This look reflected the late 1970s styles when designers like Calvin Klein and
Perry Ellis came to prominence. In the fall of 2004 Costa introduced washed silk dresses and black wool felt coats. The clothing was given weight by the librarian brogue heel. The style was exceedingly popular during both the
Paris, France and
Milan, Italy shows. In his collection for Spring 2005 Costa showed a sea-green silk dress "wrapped like a towel". The silk dress was coveted by many buyers and shipped to stores in the late fall and early winter. The inspiration for this collection's uncomplicated evening dresses were primitive wood sculptures by
Brâncuși. They were based on a trapeze, combining viscose jersey with silk.
Vogue and ''
Harper's Bazaar'' named
Elle Macpherson to their 2005 best dressed lists after she wore Costa's lime green dress. Costa's February, 2006 collection for Calvin Klein was reviewed by
The New York Times fashion critic
Cathy Horyn, for conveying "largely a surface beauty". It featured dresses with many layers of black chiffon and tulle. His collection was reminiscent of the 1930s. Horyn wondered if many women would not find the fashions "untenable and fussy, if not stifling." In May 2006 Costa served as chairman of a benefit for the
Whitney Museum of American Art. He approached artists Ghada Amer, Vik Muniz, and Billy Sullivan to make art identified with fashion. After being shown at the Whitney Art Party, the work was moved and displayed in the windows of the Calvin Klein boutique on
Madison Avenue (Manhattan). ==Private life==