The numbers behind gold farming

So how much money are these gold farming companies making? Good data are hard to come by, but PJ from MMOBux did some estimates based on PayPal data. According to those data the top company earned nearly 50 million dollar in 2007 via several websites, with the second one coming in at 20 million. Lots of money, but nothing compared to the 1 billion dollars that Blizzard made.