Designer Karl Lagerfeld lost more than $2 million selling his three-bedroom Gramercy apartment for $4.5 million, records show.

Lagerfeld bought the sixth-floor flat — which comes with a coveted key to Gramercy Park — at 50 Gramercy Park North for $6.69 million in 2006. But despite putting in custom bookshelves and other personal touches, the Chanel creative director never moved in, sources said.

By 2011, he was trying to sell the unit for $6.5 million and finally unloaded it last month for $4.5 million, records show.

The 2,150-square-foot home’s buyer is investment bigwig Sebastian Barrack. But it gets poor natural light and has high maintenance — $7,439 a month.

The apartment includes an entry foyer, views of Gramercy Park, a chef’s kitchen and a master bedroom suite with a walk-in closet.