Ever wondered how those directory enquiry services can afford to advertise so much?

UK directory enquiry services recently raised their prices such that the most popular one now costs a minimum of £9.
A bunch of UK media have jumped on these high prices and now the telecoms regulator Ofcom, which has thus far resisted calls to cap the prices these services charge, seems ready to seriously think about looking into it. While it could be argued that nobody is forcing anyone to use those services, the concern is that non tech-savvy people are being exploited.
The current