It seems that this year the ICM Registry, owner of the domain .xxx, will collect about 200 millions of dollars, with 230000 .xxx sold
http://www.thedailybeast.com/articles/2012/11/13/how-xxx-porn-s-domain-name-made-hundreds-of-millions.html
http://www.thedailybeast.com/articles/2012/11/13/how-xxx-porn-s-domain-name-made-hundreds-of-millions.html