There is a way in my mind
Add logic to get the name of the application, which with the help of your SDK also adds some logic to send this name to you through the API or in any other way that you prefer.
Once you get a new name in your server database, you can open the AppStore in iTunes and find the application there, and yes, you will find out if they pay or for free!
I know it tough if your SDK will fly with many applications, but not difficult.
An alternative way, if there is a way to find out if the application is paid or free, you can do the same, send the name of the application and its price data.
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