If a business book sells 10,000 copies, it is considered a success. It is very rare for a business book to have blockbuster success like a Da Vinci Code or the latest Harry Potter. One exception is Good to Great by Jim Collins having sold over 1,000,000 copies.
I found that out recently and it really surprised me. I am not sure why. I guess I looked at my bookshelf and saw an awful lot of business books.