A comprehensive study commissioned by the Justice Department looks at the economics of selling sex.

Though prostitution has the potential to be lucrative, most sex workers rarely reap the benefits of their revenue, according to a new report on the economics of sex work.

The study commissioned by the Justice Department looked at the underground commercial sex economy in eight major U.S. cities—Atlanta, Dallas, Denver, Kasas City, Miami, Seattle, San Diego and Washington, D.C. Researchers conducted 250 interviews with pimps, traffickers, sex workers and child pornographers—many of whom were serving time—about their business dealings in those areas. They found that the illicit sex economy had an estimated worth of $39.9 to $290 million in 2007 in each city. Atlanta was the most profitable city, and Denver was the least.

Pimps and traffickers raked in between $5,000 and $32,833 per week employing an average of five sex workers at a time (with a high rate of turnover). They charged johns an average of $150 per hour—a price point that was consistent across the country—though prices could vary depending on the age, race and drug use of the sex worker. Half of the pimps interviewed advertised online, and one fourth of those interviewed used sites like Backpage.

But pimps and prostitutes’ expenses are high, and they saved little from their earnings. Pimps can spend thousands on hotel rooms and shopping sprees for their employees, according to the report. “Prostitution and pimping — in many cases that’s not particularly profitable,” Amy Farrell, a researcher not involved in the study at Northeastern University told the New York Times. “Some parts are more marketable than others.”