I've been blogging for 10 years, and I've written over 800,000 words in posts. As time progresses, I try to clearly convey more information with fewer words. It's been hard to quantify the value derived from those words, however, since the only measurements I could make (e.g. a small amount of ad revenue) have been subjective at best.
For almost seven months, I've been writing Ansible for DevOps, publishing on LeanPub as I write. In that time, I've written ~41,600 words (with roughly 60% of the book complete), and have had ~800 readers purchase the book (either standalone, or in a bundle).