Dynamic software updating provides many benefits, e.g. in runtime monitoring, runtime adaptation to fix bugs in long running applications, etc. Although it has several advantages, no quantitative analysis of its costs and revenue are available to show its benefits or limitations especially in comparison with other software updating schemes. To address this limitation in evaluating software updating schemes, we contribute a quantitative cost/benefit analysis based on net option-value model, which stems from the analysis of financial options. Our model expresses the relation between added value and paid cost in mathematical forms. We have used this model to evaluate the revenue from dynamic updating in two case studies featuring Xerces and MobileMedia. These studies reveal the set of parameter values that render dynamic updating effective. We also compared two previously published dynamic updating schemes and observed how the perceived performance and coverage of different updating systems affects their relative gain.