Right now all members that logged time on a Jira project are summarized in Cost tracker overview. You can only workaround to set the rate of those not to be included to 0. It would help much to define a Team (or used the already defined ones!) for which you want to see the costs. Jira filters are no option as several people can work on several items and log time for the same item.
|Tempo Products||Cost Tracker for Tempo Timesheets|