“…It should be noted that the sustainability of high-quality knowledge provision on these platforms becomes a crucial issue because the generated knowledge will become public goods (Rice et al , 2019). Many online knowledge-sharing platforms recently have attempted to provide paid knowledge services to meet knowledge seekers’ needs (Cai et al , 2018; Zhang et al , 2019; Zhao et al , 2018) such as Quora Knowledge Prize (USA), Skillshare (USA), Zhihu (China) and Zaihang-Yidian (China) (Qi et al , 2019). The emerging paid knowledge services has facilitated knowledge-sharing economy, which makes it possible for experts in different professional areas to trade their high-quality knowledge for money (Qi et al , 2019; Sun et al , 2018; Zhao et al , 2018) and for knowledge seekers to access to high-quality external knowledge sources based on online payment.…”