Price deflation is rearing its head in the world's richest cities, and it's affecting an unlikely sector: commercial sex work.

A recent survey conducted by The Economist, covering 84 cities in 12 countries, found the hourly cost for a female prostitute dropped more than 23 percent over the last eight years.

Focusing on 190,000 online sex profiles around the word, the study said the average cost per hour had dropped to $260 in 2014, compared with an average cost of $340 in 2006, The Economist reported.

Citing residual effects of the 2007-2008 the financial crisis and an influx of poorer immigrants to richer nations, the study said the U.S. and large cities in rich countries had the highest number of sex workers.



On another note, the shift toward online sex advertising has lessened the need for workers to pay intermediary costs such as brothels, agencies, pimps and madams, which could mean their incomes may not have fallen as much as the price decline suggests.

Click here to read the full report from The Economist.

—By CNBC.com