inger-songwriter Madonna has become the first billionaire female pop star. A successful world tour and a string of business deals last year pushed her net worth past 650 million pounds ($1 billion), reports thesun.co.uk. The 54-year-old joins an elite club of super-rich celebrities, including director Steven Spielberg and chat show host Oprah Winfrey. Last year was the most successful of her career, as she raked in an extra 200 million pounds. Two million people watched her MDNA tour, which was the most successful of any artist in 2012. She also has a perfume range, clothing line and health drink.