Summarization may facilitate students to understand articles deeply by constructing gist, while keywords may scaffold students to reorganize the gist when summarizing articles. For this reason, this study adopts keywords to scaffold students to write summaries. Furthermore, this study also attempts to transform summarization into a group-based educational game by incorporating auction mechanisms in order to facilitate students motivation. This paper reports a case study for exploring the feasibility of three auction mechanisms, i.e. fixed prices, open bidding and secret bidding. The results shows how eight graduate students choose and bid for keywords, as well as use keywords in their summaries. The results also show their most and least favorite auction mechanisms as well as their reasons.