The first factor any business owner will have to specify is the kind of app you want to be made. Some apps are purely business apps, so they can assist users in financial transactions. But other apps are for leisure and entertainment so you can expect to find game apps and apps for travelers in this category. Ironically, the business apps can be more valuable than the game apps (because business apps help bring in income for a user) but game apps may be more expensive to develop. So be sure you are certain about your choice of app to be made.
Another factor you have to bear in mind is your choice of developer for the Custom App Development project. A capable company like Prelax Infotech may be able to do better and faster work than another developer based on their knowledge and skill sets. When you talk about the knowledge and skill that go into creating a customized app, you will have to consider the design aspect, the server aspect, the coding aspect, and the miscellaneous fees aspect (which in itself will encompass debugging, project management, hosting fees, and of course possible delays). A developer like Prelax Infotech who is skilled in all these aspects is more valuable to you even if other developers come much cheaper - because you will be paying for less time at a skilled developer in the long run.