This was an article written by Cecil Adams as part of his syndicated newspaper column "The Straight Dope", in which he answers puzzling questions sent in by readers.
Corrected for inflation, have prostitution prices been essentially the same for thousands of years?
He compares some historical figures about the prices charged by prostitutes (including streetwalkers and high-class escorts). While admitting there is a huge variability, he concludes that in general, the cost of hiring a prostitute is relatively stable. "There’s reason to think the bedrock economic constant is what it costs an impatient male to get laid."