In early phases of the software development process, requirements prioritization necessarily relies on the specified requirements and on predictions of benefit and cost of individual requirements. This paper induces a conceptual model of requirements prioritization based on benefit and cost. For this purpose, it uses Grounded Theory. We provide a detailed account of the procedures and rationale of (i) how we obtained our results and (ii) how we used them to form the basis for a framework for classifying requirements prioritization methods. Key words: Requirements Prioritization, Software Economics, Non-Functional Requirements, Quantitative Prioritization, Grounded Theory