Forbes mag lists JKR as the only woman billionaire and author fr UK.

http://www.forbes.com/2007/11/20/billionaires-britain-cavendish-biz_cx_pm_1120ukbillies.html

Rowling is the only author on our list. The seventh (and last) installment of the Harry Potter series, Harry Potter and the Deathly Hallows hit bookstores in July and worldwide sales of the first six topped 325 million copies. The film series, from which Rowling enjoys a cut of royalties and merchandising has grossed $3.5 billion, and there’s no doubt three more movies to come.