The cost of developing an e-wallet app can vary depending on various factors such as the complexity of the app, features, and functionalities offered, development time, and geographic location of the development team. A basic e-wallet app can cost around $10,000 to $20,000, while a more advanced one with additional features such as integration with third-party services, security features, and customized user interface can cost upwards of $50,000 or more. It's important to note that the cost of developing an e-wallet app is a long-term investment that can generate substantial revenue in the future.