Feature content in system releases tends to be prioritized using limited amounts of qualitative user input and based on the opinions of those in product management. This leads to several problems due to the wasteful allocation of R&D resources. In this paper, we present the results of our efforts to collect quantitative customer input before the start of development using mock-ups and surveys for a mobile application developed by Sony Mobile. Our research shows that (1) collecting quantitative feedback before development is feasible, (2) the data collected deviates from the original feature prioritization, i.e. it is beneficial and (3) the data gives further insight in requirement prioritization than a qualitative method could have provided.