Investment on usability engineering is believed to offer a variety of benefits. Some major benefits, for corporations, identified in the literature include reduced development time and cost, decreased maintenance and support costs, and increased revenue and market share. For product end users, the main benefits cited include increased efficiency, effectiveness, and user satisfaction. However, as with all investments, there are costs incurred. A problem arises when the costs incurred have to be justified against the benefits obtained. There are certain metrics used such as Return on Investment on Usability and Total Cost of Ownership. Unfortunately, these metrics rely mainly on models with many subjective assumptions to estimate the costs and benefits of usability improvements. These assumptions generally depend on the experience of the usability practitioners which may produce unreliable, inconsistent and occasionally vague estimations. Moreover, case studies showing substantiated data on the costs and benefits associated with usability improvements appear to be scarce in the literature. The objective of this study is to conduct a thorough literature review on usability cost justification to isolate critical information, by employing the State-of-the-Art-Matrix analysis. This paper explores trends in research on usability cost-justification and identifies reasons for unreliable and inconsistent cost-benefit analysis. Copyright, American Society for Engineering Management, 2011.