The recently published PEOPLE magazine extra, “All About ‘Sex and the City,’ ” is obviously a collector’s edition. It has zoomed in value — despite the fact that the special issue is still on newsstands. Carrying a cover price of $3.95, a single copy of the issue sold over the weekend on eBay for $26.50. Bidding had started at $9.99 and went on for five days. The identities of the seller and the buyer are not clear from the eBay site, but the winning bid came out of Greensboro, N.C. Among the behind-the-scenes stories inside the issue: The Girls, The Men, The Clothes, plus an inside look at the way they live. This includes a shirtless shot of costar Kyle MacLachlan, 42, at home with his pet Labrador, Coco.