The connector add-on is free, but doesn't do much more than providing the connection between JIRA and the Flapps application.
For questions about the Flapps application, I would refer you to the applications website and/or its vendor.
According to https://marketplace.atlassian.com/plugins/jira-to-flapps-connector/cloud/overview, the add-on is free:
So it looks like the only costs would be what is published at http://www.flapps.com/pricing/
There are contact details for the vendor here: https://marketplace.atlassian.com/vendors/1210617
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