Without a careful definition phase, the cost of a software project is hard to predict. The definition phase consists of analysis, architecture and design. It's an iterative process. The concept of a minimal viable product (MVP) is the minimum set of features that are required for the application to be useful.
The definition phase is typically about 20% of total project cost and 30% of project duration. The result is a Software Requirements Specification (SRS).
Based on decades of experience, the SRS can be used as a basis to estimate project cost and schedule. The number of requirements provides a project scope that can be compared to other projects. The nature of custom software development is high variability. That said, here are some typical project costs:
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