Information about accommodation must be shared with or between the girls though?
Do you think only punters have their forums to discuss this business, and that Russian or Romanian girls don't have their own message boards where they can share tips, get advises, seek flatmates, discuss agencies, countries, towns, customers?
I can't be sure about the situation in London; some here said that Diva girls actually told them that Diva took only 30%, but in other places, Paris for instance, the agency systematically provides the whole package - flights, city travels, security, flats - and takes a global cut of 50%. Well, 49% more probably, to avoid to cross the standard threshold of illegal pimping. So Diva might well take 30% and then charge the girls with the flat on top of that, at least for those who don't have their own accommodations. Depending on the country and agency, they also charge for "paperworks" when they join the agency and then when they travel (visa fees and the like). Photoshoot costs seem also quite high compared to Russian wages.