Park Slope can say goodbye to its hippy family-friendly vibes. The neighborhood, which is at the forefront of gentrified trendiness, is now home to bankers and other high earners who can afford to pay jaw-dropping prices. Roughly one in seven Park Slope family apartments now leases for more than $10,000 a month, and one in 15 leases for more than $15,000 a month, according to real estate developer Sam Eshaghoff, founder of West Egg Development, whose firm analyzed rental data . At the highest end, on the Gowanus side, three-bedrooms are going for $10,666 a month, Eshaghoff found. The park side is the most expensive on a median basis with a rent of $8,091 per month. At 366 6th Avenue, this five-bedroom townhome rents for $18,500 per month after only 10 days on the market. Courtesy of Compass A townhouse at 787 Carroll Street is asking $10.25 million, nearly $5 million more than it sold for last year.…