Bill de Blasio's campaign message, often characterized as "class warfare," seems to have united New Yorkers across the income spectrum. He actually did slightly worse with the most downscale cohorts (where there was more support for also-ran John Liu who ran to his left) than with the more upscale ones, but he won across the board.
Now of course we have a truncated scale problem here. I've heard some folks say that $200,000 doesn't make you rich in New York. That's a mistake. The median household income in New York City is $51,270. If you're earning over four times as much as the median family in your city, you're pretty rich. But NYC has an extreme fractual inequality situation, and the gap between the $200k crowd and the $2 million is very real to folks languishing with "mere" six-figure incomes. De Blasio's campaign has proposed raising taxes on marginal income above $500,000 a year. Only a very narrow slice of the city has that much money—too narrow a slice to show up in the exit poll. What you do see in the exit poll is that this idea of soaking the very rich unites a broad spectrum of New Yorkers whose economic circumstances vary quite a bit.