NEW YORK: They are as close as Americans can come to royalty, and the price at which people are acquiring momentos and pieces of their lives certainly reinforces that impression. Part of the Jacqueline Kennedy Onassis estate is up for sale at New York's venerable Sotheby's auction house in a four-day marathon sale. Well into its second day, the sales have exceeded even the auctioneers wildest expectations: a walnut humidor, a gift to President Kennedy from the comedian Milton Berle that was expected to sell for $2,000 to $2,500 went for $574,500; $442,500 for an oak rocking chair used in the Kennedy White House; $48,875 for a Tiffany silver tape measure engraved with Mrs. Kennedy-Onassis' initials. The list goes on, each item far exceeding the expected sale price. Thus many who had made the trip to an auction house for the first time in their lives in the hopes of owning a piece of Camelot quickly saw their hopes outbid by the frenzied buyers. Bruce Wolmer, editor in chief of Art & Auction, predicts the Onassis sale will far exceed Sotheby's 1987 Duchess of Windsor jewelry sale, which brought in $50 million. Mrs. Onassis' jewelry goes on sale Wednesday night and includes a 40-carat diamond she received as an engagement gift from the Greek shipping magnate. Sales later in the week will include JFK's golf clubs and Mrs. Onassis' 1992 BMW.