Cruises and The Yachts of Seabourn. supplement and guests will be provided with a revised final payment amount. the fuel supplement could be re-instated if oil prices increase significantly. the NYMEX ( New York Mercantile Exchange Index ) increase above $ 70 per barrel. the selection of a vacation in the current economic climate , " Harber added. fourth guests ( not to exceed $ 56 per person per voyage ) .