If your app requires a subscription to "turn off my display" or other basic features of the phone itself, I'm not using your shitty ransom app.

I’m starting to suspect 99¢ isn’t a sustainable price point.

I don't see how an unsuccessful app will gain revenue if it changes to an unsuccessful subscription scheme? And 0,99 Euro seems legit for apps like Flappy Bird or some one-trick-ponies.