BusinessWeek Online – For months, high-end retailers posted healthy sales increases, thumbing their noses at dismal reports of slumping home sales, risky mortgages, and rising energy prices. But now it looks as though even well-heeled consumers are pulling back. On Jan. 10, the upscale department store Nordstrom said that December sales at stores open at least a year fell 4% from last year, compared with an 8.7% increase in November. Saks , New York’s Fifth Avenue luxury mainstay, also reported that its same-store sales were up a mere 0.8%, compared with a 25. …