The island of Manse-hattan t

It’s going to come as no surprise that the city’s priciest properties are in Manhattan, but a new study shows the borough accounted for fully 86 percent of all home sales for more than $2 million over the past three years.

Just about all the rest of the pricey pads — 13 percent — were sold in redhot Brooklyn.

That left the other three boroughs splitting a mere 1 percent of the high-end market.

Soho, Tribeca, Civic Center and Little Italy topped the list of neighborhoods with $2 millionand-above sales last year.

All other neighborhoods in the Top 10 list were also in Manhattan.

On the flip side, 11 neighborhoods had just one home sale last year in the high-end league — including Astoria in Queens; Bath Beach in Brooklyn and Great Kills in Staten Island.

Between 2014 and 2016, 11,973 properties in the city exchanged hands for $2 million or more — 8 percent of all homes sold during the period.

The Independent Bud- get Office came up with the figures in response to questions raised by Manhattan Borough President Gale Brewer, after Mayor de Blasio began prodding Albany to approve an added 2.5 percent tax on sales of homes in the city for $2 million and up.

The mayor said the surcharge — which he dubbed a “mansion tax” — would raise $336 mil-lion in fiscal 2018 to subsi-dize But senior Brewer housing.said the findings show that her borough would have to shoulder most of the burden.

“I am against Manhattanites being the cash cow for the entire five boroughs, which is what this sounds like,” Brewer told The Post.

“We all want the seniors to have homes . . . but it doesn’t have to come from this tax,” she added.

De Blasio paired the proposed tax with seniorhousing subsidies in the same way that he marketed a 2014 proposed income-tax hike on the wealthy to expand universal pre-kindergarten.

The mayor got the funding for pre-K from Albany in 2014 — but without the tax hike. And Albany leaders have shown no appetite for his latest proposal.

“We don’t like raising taxes; we like cutting taxes,” state Senate Majority Leader John Flanagan (R-LI) said last month. “In my opinion, a mansion tax is a nonstarter.”