Done right, a blog is a very cheap and powerful marketing tool. As @superasn has mentioned, 1 huge win (again if done right) is you can keep getting recurring

Done right, a blog is a very cheap and powerful marketing tool. As @superasn has mentioned, 1 huge win (again if done right) is you can keep getting recurring signups / new users if 1 or more of your blog posts ranks on top for keywords relating to your web app / product offering. I've successfully grown a blog to over 100K monthly visitors in less than 6 months, all using organic SEO techniques. Too bad I didn't (still don't) have a product to market on that blog. It ranks on 1st page for several tech related keywords, incl. a couple related to apple and steve jobs. What's your web app / domain? Without knowing much about it, I can't give you domain / topic specific advise. My email is in bio if you wanna chat more.