A storied penthouse perched atop one of Manhattan’s most exclusive addresses has returned to the market for the fifth time — and for quite a discount. Now asking $19 million, it’s a stunning $26 million below the $45 million price its owners first dangled before buyers nearly six years ago, The Post has learned. The crown jewel of 1 Sutton Place South, a landmark Rosario Candela-designed cooperative on the East River, re-listed June 18 with Serena Boardman of Sotheby’s International Realty.