Like Roxie and Velma, I have three best friends and one of them has written seven books, he has published four, but he has sold approximately a thousand, which compared to, say, Nabokov that may not seem like a lot; however, when put into certain perspectives, a thousand books sold can be impressive.
For example, imagine that Amazon is a brick and mortar bookstore. Now imagine getting an email from Amazon and a bookseller informing you, "[insert author's name]. Good news. We've sold one-thousand copies of your book(s)!"
I would imagine that most authors would be pleased with that email.
That email is no different from my friend getting his historical sales report from his (very small) publisher informing him that he has sold (close to) a thousand books.
Even an email to inform an author that he or she has sold ten books is good news.
"[insert author's name]. Good news. We've sold ten copies of your book(s)!"
I've posted before that another way to put book sales into perspective is to consider each book a work of art. Most artists (i.e., writers) would be overjoyed to sell one thousand pieces of art - or even ten for that matter.