It's not just common folk tightening the belt in anticipation of the Great Recession of 2008. Socialites, those airy creatures who are thin and rich and go to parties for a living, are also starting to (gasp!) budget. At a party to benefit the East Side Settlement show last night at Mallet Antiques, Melissa Berkelhammer vowed to take the subway more often. "I'm also buying less frivolous things," she said. "I'm not paying $300 for a haircut." Berkelhammer's neighbor, Tana Dye, had a more extreme money-saving strategy: Don't leave the house. "I live in midtown, so I have to stay in my apartment. I walk out my door, and I'm in Bergdorf or Barneys."