At 56 Leonard Street, where a penthouse just went into contract for $47 million, the buyers are poised to receive a 76% break on their real estate taxes.

At 150 Charles Street, an ultraluxury development in the West Village, the tax break is 70%.

And at One57, the 90-story skyscraper in Midtown where asking prices top $10,500 a square foot, the tax break is an eye-popping 94%.

A recent review of the offering plans for some of the city’s most expensive new apartment buildings offers an interesting peak into the perquisites and disadvantages of a lavish lifestyle. There are the windfalls, like the generous tax breaks, but there are also oft-overlooked expenses, like mandatory health club and dining-room fees, that can add to a buyer’s bottom line.