Developer console app

Hi Team, 

We are trying to provide dropbox support into our existing application which uses file-stack for uploading files.

We followed this tutorial and created an APP from the developer console. 

Currently our app (dropbox developer console) indicates it is in development mode and supports maximum of 500 users although it freezes once it reaches a count of 50 as per documentation.
From the same documentation https://www.dropbox.com/developers/reference/developer-guide we also got to know that we need to proceed with 
"Apply for production" CTA in order to take our app to the production where any number of users can be connected to the app.

We just wanted to understand if we want to "apply for production" where n number of users can connect to app,
Are there any charges involved in this ?

Awaiting your response 

Regards,
Rohit Raut