App Development Questions
With the core proposition at hand (which is, in this case, enabling sales through an app), you should be able to test the market and see if there are enough customers to buy. To help improve your idea, remember to ask for feedback from your customers.
Remember though that there are many other ways in which you can make money out of an app. Charging for downloads is just one of them. Make sure to have a clear monetization strategy before developing your app.