We've been following the saga of Brooke Astor's duplex at the venerable 778 Park Avenue for nearly three years, but we never tire of twists and turns. A good thing, because there's another. The Post has unmasked the buyer: Swiss investment honcho Daniel Forcart, who apparently has some big renovation plans. Having seen the listing pics, we're not surprised. What is surprising about the whole thing is the rumored sale price of $19 million, far, far below the 2008 list price of $46M. Of course, Forcart's $27 million discount still needs board approval, but after a Hall of Fame performance by the PriceChopper at the Buckley maisonette downstairs, the board's probably used to discounts.