Flowsana's pricing works based on the concept of Billable Users. A Billable User is an Asana user who's a member of a team having workflow-enabled projects. Flowsana charges at $2.99/month USD per Billable User.
Say you have a Marketing team which has 6 Asana users who are members of that team. If you add Flowsana workflows to any projects in that team, you will have 6 Billable Users.
Asana guest users are not counted; like with Asana itself, you don't pay for guests in Flowsana.
If the same user is a member of multiple teams, you only pay for them once. Continuing the above example, let's say you have a second team, Sales, that has 10 members in it, and you add Flowsana to one or more of its projects. But 4 of those 10 users are also members of the Marketing team. Your resulting Billable Users will be 12, not 16, because you only pay for those 4 users once.