Per meter cost of Sailing megayachts?

As for motoryachts in the class above 50 meters the rule of thump was a million/meter length, but how expensive is a sailing yacht of comparable size actually? I read that philanderer cost about 10 million when she was built (but that was in Thailand afaik). My question is, how much for example is a Perini Navi 50 Meter SY?