How strong is the market for New York City penthouses? The owner of a Walker Tower aerie who wants $42 million for the pad is about to find out. Spanning nearly 7,000 square feet, the four-bedroom penthouse is asking $6,000 per square foot. “All the finishes have been upgraded,” said listing agent Toni Haber of Compass, who said the current owner combined two penthouses in 2014. Haber didn’t comment on the buyer’s identity, but said they are … [more]