Miami-based real-estate firm Related Group is asking $90 million for a penthouse atop the luxury condominium it is developing on nearby Fisher Island—a price that would smash all sales records for condos in the Miami area.  

Related is building the boutique condominium with roughly 50 units on the last remaining parcel of land on Fisher Island, considered one of the most exclusive ZIP Codes in the country and accessible only by ferry or other boats. Related acquired the 6.5-acre property in September for $122.6 million, with its partners Teddy Sagi, BH Group and Wanxiang America RE Group. The developers hope to break ground by the third quarter of 2023. 

The 15,000-square-foot penthouse would have its own roof deck and a private pool, grill and lounge area. While there is no guarantee the penthouse can command the $90 million asking price, Related said it has already met with 20 families interested in high-price units at the building. Most of these affluent buyers tend to pay all cash. 

Previously, Related Group had set the price for the penthouse at $60 million, but the firm ended up increasing it by 50% because, after executives there crunched the numbers, they believed that is what the penthouse is worth, Mr. Perez said. Related is asking $60 million for the building’s second penthouse, at 10,000 square feet. 

The Fisher Island project is the latest sign that even as prices for luxury residences in much of the country are coming under pressure, South Florida’s high-end condo market continues to defy gravity as developers push prices higher.

The median sales price for the Miami Beach single-family luxury market, representing the top 10% of sales, was $3.5 million—about 52% above prepandemic levels, according to a recent report from real-estate broker Douglas Elliman. 

Fisher Island represents a unique part of the luxury market, with very limited inventory built after 2010. According to broker ONE Sotheby’s International Realty, 151 units sold from January 2021 through November 2022, with an average price of $7.1 million. 

“These are people who don’t deal with mortgages or interest rates,” said Jon Paul Perez, president of Related Group. “We haven’t seen the economy have an effect on this group.” 

Even if Related marks the price down, it could still easily exceed the current record sale. Billionaire hedge-fund manager Ken Griffin paid $60 million in 2015 for a Miami Beach condo in what remains the highest price paid in the Miami area.