Is it important to get feedback from paying users for a paid app?

We make a camera app for iPhone, NoctaCam, that's paid. I haven't gotten enough feedback from users, so I've been encouraged to make the app free temporarily to get more feedback. Is it critical to get feedback from the right users -- paying users for a paid app? I've resisted making it free, because I thought that whether someone has paid is in itself an important piece of feedback, perhaps the most important. Feedback from paid users might be different from feedback from free users, and might take me in the wrong direction. But I heard the counter-argument that first you want to validate that the app is useful, by getting people to use it, because people won't use a free app that does nothing they care about. Once you know the app is useful, then you get to the next step of whether they're willing to pay for it. How should I look at this?