Of course they are, but you can get work by women cheaper. That's what a study by Art Market Research shows, though prices for women's art is going up faster than prices for men's work.
When I was an art student, Janson's History of Art mentioned no women artists at all. That wasn't too many years after this conversation, repeated in the Financial Times' story, apparently occurred:
And a famous story about Lee Krasner, the abstract expressionist painter married to Jackson Pollock and perpetually in his shadow, has it that her teacher, the renowned critic Hans Hofmann, once said of her work: “This is so good you would not know it was painted by a woman.”
By the way, the above Krasner sold for $579,200 in an auction at Sotheby's in 2003, the second highest sale at the auction (a Roy Lichtenstein went for $590,400).
Read the Financial Times story here.