In a typical citizen science scenario different groups of people take on various roles in a research process that is often coupled with educational, social or personal objectives. A widely accepted viewpoint asserts that such an endeavor should bring benefits to all involved parties and that no participating individuals should act "in service" of others or of the end goal. However, the large variety of implementation models, of participating individuals, and of desired impacts, leaves room for inconsistencies regarding what outcomes count towards mutual benefits. In this article we examine the ambiguity embedded in the definition of mutual benefits in citizen science and take a stand towards its resolution. We use school-based citizen science as a model for a multi-stakeholder, multi-objective citizen science. Focusing on teachers and scientists that work together to facilitate student participation in citizen science, nine teacher-scientist pairs that collaborated on nine different school-based projects were included as study participants. We examined participants' motivations for school-based citizen science and perceived costs and benefits using a questionnaire that they filled while verbally explaining their answers. Our findings reveal multiple ways in which teachers and scientists tapped into their professional, social and personal identities to create multilayered sets of motivations and perceptions of benefits. Thus, we argue that a mutualistic perspective of citizen science should take this complexity into account and be prepared to answer multi-faceted expectations, which may reside not just among but also within participating individuals.