I see many companies and developers making some mistakes, as it seems:
Mistake One: Asking for money even before the user got a chance to use the app: I wouldn't pay for an app when I don't know how well it will work, and whether it will be useful to me at all. Reading a description or watching a video is no substitute for using the app.
The solution is to let people use your app and see what a high-quality app it is. Let them integrate it in their workflows and in their day-to-day usage. Then ask for money, and they'll be more willing to pay.
Have a generous trial period, like two months. Or, better, a usage-based trial, like an email app letting users read 1000 mails or send 100 before asking for payment.
Mistake Two: Withholding features from users: This usually happens with freemium apps, where some features are free, while others require payment. As Marco points out, most people will use the worse, crappier version of your app. Would you be happy with that? I wouldn't. I would want every single user to use the best version of my app .
The solution is ads or subscription.
Mistake Three: Locking paying users into old versions: You buy an app, and the developer later releases a new version. And you're stuck with the old one. Ironically, free users are always on the latest version of the app. It's counterintuitive to penalise paying users. It discourages them from paying again for your apps, or for apps in general.
The solution is not to sell a license to a specific version of your app. Sell a license to your app. Like a subscription. Or ads.
Mistake Four: Showing ads first, and then asking for payment to remove them: Ads are often animated, distracting me from what I'm trying to do, and annoying me. And once I'm annoyed, I wouldn't pay the developer. Having ads in an app also advertises  the app as being low-quality. Why would I pay for a low-quality app?
The solution is for an app that offers both options to not show ads during a trial period. After the trial, ask the user to pay and only if they refuse, show ads.
If you're making an app, consider avoiding these four common pricing mistakes.
 If a feature isn't helpful to a significant fraction of users, or is only peripherally connected to the main purpose of the app, it shouldn't be there in the first place. As opposed to being there and available only to paying users.