Probably about £2.50.
There's often a phenomenon where you get something 'rounded' to a local currency. In Brazil, the currency is the real. Currently you get about three to the £, but it used to be more than four.
One of the mos famous Rio brothels has been described as a bit like the bar from Star Wars. The number of prossies using the place runs into four figures though they're not all there at the same time. It's a few alleyways with bars and upstairs rooms, which sounds like Bangkok's Patpong only it's much bigger, louder, less glitzy and although you can opt for a 'carry out' most business is done on the spot. Many mingers of course but gems as well. But prices are getting out of hand now, and they can ask 30R or more.
Cheaper are the downtown shops. Noisy brothels over several floors, each with one or more businesses where you choose a girl from the bar or the line up. There's a 10 minute minimum so that's just over £3 in today's money but more like 2 or £2.50 a few years back. These places are in the business district so you can coke up on 'vitamins' with a breakfast, pop two or three, have an upmarket lunch a few doors away and then go back for a beer and and afternoon shag. Fast-food sex proliferates in other places like Belo Horizonte rather on the dedicated motel building model, that cheapskaters in Germany will be familiar with. A whole street or so is filled with old, disused, multistorey, low-grade hotels. Each room has a hooker, each hooker charges about the same - 1R a minute.
But before anyone rushes out there, I must remind you that Brazil is now one of the more expensive holiday destinations. You will pay so much for your flight and accommodation that the small change hooker shops, although only charging the equivalent of two or three local bus rides, are not only the least of your worries but will be avoided by most tourists anyway. If you can afford Brazil these days you no doubt want to bask in places there that £200 an hour is nothing.