ICELAND BOUND: Francisco Costa is headed from one extreme to another this week. A quick visit to Stanley Korshak in Dallas marked his first visit to the city in nine years, but it was merely a stopover on his way to Reykjavik for a four-day inspirational sojourn. “I don’t have a favorite place to vacation — I always like to go somewhere different,” he said. In Dallas, it was all Champagne, chardonnay and smiles from a cadre of women who were impressed by the craftsmanship of the spring collection. “You can see why it’s $15,000,” said Susan Posnick, eyeing a pieced snakeskin coat. Posnick and other socials greeted the designer Tuesday evening under the buffed Venetian plaster ceiling of Karla McKinley’s manse, and then visited the designer at the store the following day to see the spring collection.