In 2006 I published a book – Knowing Knowledge – (.pdf version for download here). I’ve never really tracked how many copies it has sold – a few thousand at best. I stopped tracking pdf downloads about two years ago as it was approaching 1 million (far, far less have actually read it, I’m sure). It has been translated into various languages (Spanish, Chinese, and a few others that I forget at the moment). All of this to say: open publishing is far more effective for disseminating ideas than traditional publishing. A recent publication from Rory McGreal and Nian-Shing Chen, A Comparison of an Open Access University Press with Traditional Presses (.pdf), resonates with my experience from an academic perspective:
Results suggest that there is no significant difference in the Amazon rankings. This suggests that releasing academic books on open access does not lessen printed book sales online in comparison with traditional university presses using Amazon.com and Amazon.ca rankings. On the other hand, AUPress, because it is open access and publicly available at no cost, can boast of having a significantly larger readership for its books. The traditional university presses, because of their cost, print-only format, and other proprietary limitations are not readily available and therefore not accessible to many potential readers.
Quite simply: if you’re publishing, think beyond the financial impact of a book. Consider peripheral factors such as extending the reach of your work and non-monetary reward factors such as connecting with colleagues in emerging economies, speaking invitations, collaboration opportunities, etc.