In another sign of the skyrocketing costs of buying a home in New York City, a new report found that the number of neighborhoods with a median sales prices of $1 million and up more than quadrupled in roughly a decade, rising to 17 from 4 in 2010.

In a study released Monday, Streeteasy shows exactly how many neighborhoods have been swallowed up by high-priced housing over the years. Leaving out neighborhoods dominated by large homes where the median price per square foot is below $1,000, it found that back in 2010, there were only four neighborhoods with median prices above $1 million. All were located in Manhattan: Soho, Tribeca, the Flatiron and Chelsea.

But over the last nine years the list has grown to include five Brooklyn neighborhoods: Brooklyn Heights, Greenpoint, Park Slope, Prospect Heights and Williamsburg.

"Despite the recent slowdown, the cost of entry to homeownership in New York City continues to move further out of reach, with prices increasing the fastest in the most affordable neighborhoods," said Nancy Wu, an economist at StreetEasy, in a statement. "Those with the means to buy in Manhattan are increasingly looking to the outer boroughs for more space for their money, causing the amount of relatively affordable inventory to shrink and forcing prospective buyers who are on a budget to ride the train further and further from the city’s center to find something they can afford."

As an example, Wu noted that in Prospect Heights, the median price of a home was $536,000 in 2010. Today, the neighborhood boasts a median sales price of $1.16 million—more than double what it was nine years ago.

Similarly, the Lower East Side, which came in at $1.4 million, crossed the million dollar threshold for the first time this year. In making that leap, sales prices ballooned nearly 40 percent in just one year, from $993,000 in 2018.

The million dollar mark has long been used as a barometer of New York City’s real estate market. In January, reports that Manhattan had dipped below the $1 million median sales price at the end of 2018—the first time that happened since 2015—was taken as a sign of the gradual cooling of housing prices in the city.

All told, Manhattan has 11 million-dollar-plus neighborhoods, led by Tribeca, which is the priciest New York City neighborhood by far, with a median sales price of $4.1 million.

Whether such prices are sustainable is up for debate, especially as some experts predict a recession on the horizon. Monday's report comes on the heels of a more provocative Streeteasy study that found that one in four new luxury condos built over the last six years are unsold. While prices have risen substantially, the Lower East Side was cited as the city neighborhood with the lowest percent of new condo sales. The report blamed its standing on One Manhattan Square, an 80-story tower whose 815 apartments have struggled to sell. Developer Extell has tried several eyebrow-raising strategies to entice buyers for the units, which start at $1.2 million. Last week, The Real Deal reported that the company had announced a rent-to-own program, in which renters can apply one year's of rent toward the purchase price. Prior to that, it dangled an unprecedented incentive in the form of a 10-year waiver of common charges on the priciest units.

“The model of ‘If you build it, they will come’ is over,” Jordan Sachs, a broker at Bold New York, told The Real Deal. “People aren’t believers now,” he added. “There’s a lot of talk about a recession on its way.”