Brokers are raising eyebrows over Related Companies honcho Stephen Ross’s bold $75 million ask for his roughly 8,500-square-foot Time Warner Center penthouse.

The latest sellers at the building sold at a loss of more than $5 million.

They bought their 68th-floor, 4,050-square-foot unit for $19.45 million in 2012, spent money renovating it, and sold it for $15.7 million — a sizable loss — in June.

The 92nd Street Y has signed a lease to rent a 1,000-square-foot space on the ground floor of the tall tower under construction at 180 E. 88th St., developed by DDG and Global Holdings.

The space, which will have its own entrance, will be used for community-based programming such as youth and adult dance classes.