Nina’s is a small Upper East Side eatery, dependent on family labor to turn an extremely modest profit from serving 300 meals a week in its 24-seat dining room.

The dense city’s crowds of customers mean that goods can turn over faster than anyplace else in America

The high-end sex shop buys from tiny artisan-type vendors, making for an upscale clientele and an average 63 percent markup.

The most-profitable yoga studios are efficient: They fill four to five classes daily, plus private classes.

A fifth of the city’s food pantries and kitchens have budgets of zero—they run on food donations alone.

The Upper East Side institution is caught between customers expecting low prices and ever-rising food and staff costs, made more difficult by a giant menu.

Lawyers, insurance companies, and private citizens hire McKeever for a base rate of $100 an hour.

With data on petty drug dealers, the economist Steven Levitt has taught us that there is an abundant supply of people willing to work in the drug industry at near the minimum wage.

Taxis become economically attractive when the cost of paying someone to drive for you is less than the costs of storing your car.

How do you improve on water? Pricey new magic potions on tap.