Designer Markup on YSL's Paris Apartment?

Legendary fashion designer Yves St. Laurent's duplex apartment at 55 Rue de Babylone on Paris' fashionable Left Bank hit the market this past week for $34.6 million. This listing price reflects what appears to be a substantial markup from the $18 million valuation that was cited for the same property this past spring, when French President Nicolas Sarkozy and Carla Bruni-Sarkozy were reportedly seen viewing the apartment as a potential lovers' retreat from their official Elysée Palace-residence.