DriveWatcher pricing is calculated based on the number of subscriptions purchased for the team, not by its number of members.
If you are using the Free Plan of DriveWatcher, you will not be billed. However, you will not be enjoying all the features DriveWatcher provides.
Once you add the payment information, you will be charged 2.50 € for each subscription you activate.
In case you enable the «Auto-increment total subscriptions» setting, you will be able to create subscriptions without a limit, and you will be billed according to the maximum number of active subscriptions during the month.