"These are my Mercedes Benzes," says Radisson Seven Seas Mariner's German-born chef Tobias Schreiber, pointing to the $850 tins of sevruga caviar that he keeps in the ship's cold-storage room, where the cheeses are also kept. At his Signatures restaurant, Schreiber uses these luxury ingredients for dishes like sevruga caviar with celery root, foie-gras remoulade and caviar-lemon sauce.