I have heard some people use the term, for example in this video but I cannot find a precise definition of the concept online.
What is soft ROI?
According to this site :
Though the soft business ROI does not show up as a bottom-line savings, it can be gauged by the efficiencies of a system that responds to business transactions in real-time. Soft ROI also manifests itself as a return in intangible elements, including faster time to market, competitive advantage, brand strength, and customer experience and satisfaction.There is another site I think mostly developed to discussion of topics of ROI, which has this to say about Soft ROI To make a long story short from what I have gathered. Soft ROI would be something that cannot be quantified by tangible means like money, assets, lines of code for software, etc.