In recent years, mobile phones have become an increasingly important component in survey data collection. This holds true for self-administered questionnaires and particularly for interview surveys, where mobile phones enforce the combination with other survey modes. However, whether to include mobile phones in a particular survey design depends on complex cost—error relationships. To address this issue, the authors elaborate a metric—based on a product of costs and estimates of survey errors—that is then used for post survey comparison of design alternatives. The authors illustrate this approach with a simulation study using parameters from empirical research. The results show that such evaluation can potentially change the selection of the preferred design option compared to situations where only some of the components (e.g., response rate, nonresponse bias) are used for evaluation. More specifically, the decision about the inclusion of mobile phones predominantly depends on their bias-removing potential, while it is much less sensitive to changes in costs and other error parameters.