Jeg tror det er gratis

Edit:

Jeg var lige inde og kigge på MitID hjemmesiden. De skriver selv at der ikke var noget problem uden play integrity. Men at de implementerede det alligevel:

Therefore, an integrity check is now being introduced to ensure that the MitID app is downloaded from the certificed Google Play or Apple App Store, and to check whether Google or Apple consider the phone the app is running on to be compromised or not. This is happening even though there are no known cases of fraud with fake MitID apps.

https://www.mitid.dk/en-gb/about-mitid/news/mitid-gets-an-extra-anti-fraud-mechanism/

As the much more timely reply indicates, it is quite free