How much is Flow app?

Could you please clarify for me? I'm trying to understand the pricing structure of the Flow app. Could you tell me approximately how much does it cost to use the Flow app? Is there a one-time fee or is it subscription-based? Also, are there any additional costs or hidden fees that I should be aware of? I'm just trying to get a general idea of the financial commitment involved in using this application. Could you provide some more details on the pricing? Thank you for your assistance in this matter.