From free to fee: users' knowledge payment behavior in knowledge-sharing platforms

Purpose Drawing on self-expansion theory (SET), this study aims to uncover the psychological process driving the transition from free to paid engagement in knowledge-sharing platforms. Specifically, it examines how platform characteristics influence user attachment and investigates how such attachment subsequently affects willingness to pay (WTP) and actual payment behavior. Design/methodology/approach This study adopts a longitudinal field research approach for data collection and selects Zhihu as the knowledge-sharing platform to collect data. By combining questionnaire surveys with secondary behavioral records, 274 users' subjective perceptions and objective payment behavior data were collected over time to test the proposed model. Findings The results demonstrate that the perceived quality of free content and collective efficacy significantly strengthen users' attachment to both the platform and content creators, which in turn promotes their WTP and actual payment behavior. Post hoc mediation analysis further reveals that these effects operate through a sequential psychosocial pathway. Additionally, exploratory multi-group analyses (MGA) indicate that the core mechanism remains robust across gender and usage patterns, albeit with potential nuanced differences in specific pathways. Practical implications The findings advocate a strategic shift from transaction-focused to relationship-centric platform management. Practitioners should cultivate user attachment by (1) investing in high-quality free content and fostering collective efficacy, (2) tailoring engagement strategies to different user segments along the psychological pathway from attachment to payment and (3) adopting an experimental, data-driven approach through industry-academia collaboration to refine monetization tactics. Originality/value This study extends SET to the context of knowledge-sharing platforms by conceptualizing knowledge payment as an investment in a self-expanding relationship rather than a transactional exchange. It delineates and empirically validates the psychological pathway from platform resources to attachment and, ultimately, to payment behavior, providing a coherent mechanism for the transition from free to paid knowledge acquisition.