With the advent of digital technology, the persistent rise of smartphones, and the proliferation of mobile applications, the demand for iOS app development is surging. In this milieu, correctly budgeting for an iOS app development project is a critical, albeit complex, undertaking. A comprehensive understanding of all the factors involved, including timeline, resources, and technical requirements, is necessary not only for an accurate estimation but also to ensure a successful and profitable project execution.

To begin with, the very cardinal point in budgeting for an iOS app development project is to grasp the nature and scope of the application you aim to build. This requires an in-depth analysis of your app idea, its feasibility, and its potential market impact. Such an evaluation will illuminate the breadth and depth of the functionality your app requires, the complexity of its user interface, and the resources necessary for its creation and maintenance.

Secondly, it is essential to consider the developmental methodology to be employed. Two primary developmental methodologies exist: waterfall and agile. The waterfall method is a sequential design process where progress is seen as flowing steadily downwards, akin to a waterfall, through the phases of conception, initiation, analysis, design, construction, testing, production/implementation, and maintenance. This methodology's strength lies in its simplicity and linearity but can lead to increased risk and uncertainty because of its lack of flexibility.

On the other hand, the agile method is an iterative approach to software delivery that builds software incrementally from the start of the project instead of delivering it all at once near the end. It works by breaking projects down into little bits of user functionality, prioritizing them, and then continuously delivering them in 2-4 week cycles called iterations or sprints. The agile approach provides greater flexibility but requires more customer involvement and can be more costly.

Third, the selection of technology stack for the app's backend (server-side) and frontend (client-side) is a crucial decision impacting your budget. The backend technologies could include Node.js, Django, Ruby on Rails, etc., while the front-end part could include React Native, Swift, or Objective-C. The choice between these depends on your app's requirements, the expertise of the development team, and the cost associated with each technology.

Next, the design phase is where you decide on the user interface (UI) and user experience (UX) of your app. The UI/UX design is a significant determinant of your app's success and plays a crucial role in user acquisition and retention. Thus, budgeting for a highly intuitive and aesthetically pleasing design is an investment in the app's market performance.

The testing phase, which often gets overlooked during the budgeting process, is indeed another key determinant of your app's success. Rigorous testing procedures ensure the smooth functioning of your app and help to fix any bugs or glitches before the app is launched. Ensuring a separate budget allocation for this phase is invariably wise.

Lastly, the budget must account for post-launch services such as app maintenance, updates, and marketing. Post-launch services are crucial for keeping your app relevant in the ever-evolving app market and ensuring a steady stream of users.

In conclusion, budgeting for an iOS app development project can be a complex process requiring an understanding of various facets, including scope, methodology, technology stack, design, and post-launch services. By taking these factors into account and by carrying out a thorough feasibility analysis, one can create an effective budget that results in a successful app with a high return on investment.

Remember: "A goal without a plan is just a wish." - Antoine de Saint-Exupéry. With an effective budget, your iOS app is not just a wishful thought but a meticulously crafted plan ready to be executed. The budget is your roadmap to success, and the journey to that success begins with knowing where you are headed and how you intend to get there. Happy budgeting!