And yet, given that every area is treated the same way, brokers acknowledge that if you look at a house in the $2 million to $3 million range (just enough to get something nice, but not enough to get a one-of-a-kind mansion), the Zillow data largely bear this out: The average price per square foot in Sag Harbor is higher than Hampton Bays, and everyone agrees that  your money would go further in the latter than the former.

Similarly, “yes, in broad strokes you will get more for your money on Shelter Island than in Southampton or Sag Harbor village right now,” says Madore. “But obviously, in every market there’s a wide swing of what you’ll get.”

So, caveats in mind, here are Zillow’s findings and the brokers’ reactions. It might not unlock the secrets of Long Island’s beachfront properties, but it’s certainly a start.

The Numbers
The most expensive area from May 2017 to May 2018, according to Zillow, was Sag Harbor, which had an average median price per square foot of $1,297. No. 2 on the list was Bridgehampton, with an average median price of $871 a square foot, followed by Southampton, with $706. Fourth is Westhampton Beach ($684), fifth is Shelter Island ($548), and sixth is Hampton Bays ($388.) Over the same period, the median price per square foot for all of Suffolk County, which comprises the entire east end of Long Island, was $338. The total for Nassau County, which covers the rest of Long Island, was $321.

The Explanation
The key thing to remember when looking at this data, brokers caution, is that it reflects what’s sold, rather than what’s for sale.

So currently, Sag Harbor is “on fire,” says Carol Nobbs, a broker for Douglas Elliman, based in Bridgehampton. “Everyone, especially Europeans, want to be able to walk into town and eat ice cream.”

In Southampton, in contrast, many of the more expensive mansions have sat on the market, Nobbs says, which can make the town seem cheaper than it actually is. Those large houses “aren’t moving,” she says. “A lot of inventory is on the market, and if you don’t price it right, it doesn’t move.”

“I deal in the world of whims and wants, not needs,” says Madore. “It’s a second, third, fourth home market. The people here don’t need to sell, and the buyers don’t need to buy.”

In a similar vein, what has sold recently, particularly in Sag Harbor, might not be representative of the overall housing stock.

“A lot of that [dollar value] has to do with some higher-priced waterfront homes that have sold in and around Sag Harbor,” says Sanders. “There was a teardown that recently sold for $10.15 million.” Also, she adds, “in the last year there was some relatively high-priced new construction in Sag Harbor Village; one 5,000-square-foot house sold for $8 million.” The price was so high, she explains, partly because “it was furnished by a designer of repute.”