This paper scrutinized online communities where users spontaneously shared their bookkeeping records. Unlike music or photos, it addressed phenomena in interacting with strangers about extremely personal and sensitive information. We analyzed why some users are willing to share data about their personal financial status and some are not. Based on our interviews, users in the online community can be categorized into four types. Regarding users' willingness to pay, we examined the motives behind the sharing of expenditure-tracking data even when a monthly fee is charged. This paper investigated the motivation and contextual reasons behind the sharing of such private and tricky data about one's financial status. Our findings explain the interaction necessary to facilitate exchange of transaction information and demonstrate that an anonymous online community can be utilized in the financial sector.