Early in my career, I was a product marketing manager and creating return on investment (ROI) analyses for customer proposals was part of my job. Now as a copywriter, the materials I write often cover ROI and other financial measurements. The challenge has always been how to present those numbers in a way that is clear, accurate, and relevant.
The book Making Technology Investments Profitable: ROI Roadmap to Better Business Cases is a detailed guide to building ROI analyses. Although it is targeted primarily to IT purchasers, this book provides valuable insight and guidance for those who market IT products. Too often, marketers use empty phrases to describe the potential value of investing in their products. The content in this book will help marketers substantiate those claims and make all of their product messages and promotional materials more credible and compelling.
P.S. You'll also find a related discussion about value propositions in my book Copywriting That Sells High Tech.