Perspective

From Publishers Weekly "A Bookselling Tail" from 2006 noting 2004 Bookscan data

80% of books sell fewer than 99 copies
96% of books sell fewer than 1,000 copies
Average American book sells 500 copies

According to Editorial Ass in 2008

Sell 7,000: "you're a star."
Sell 4,000: "strong seller."

From Association of American Publishers on publishers.org

2009 eBook annual sales up 177% overtaking audio books
2009 overall book sales down 1.8%

From Bowker

288,355 new traditional books...