By Katie Navarra A 2,500 dollar bid, now 3,000 Now 3,000, will ya give me 3,500? 3,500 dollar bid, now 4,000, Now 4,000, who will give me 5,000? The rapid-fire auctioneer’s chant at the Art of the Horse gala will prod bidders into a fierce but friendly bidding war for one of 16 life-size fiberglass