The mHealth app market is growing rapidly, with over 50,000 apps on major platforms and a projected market value of $400 billion by 2028, highlighting the importance of understanding development costs. Costs of developing apps are influenced by stages like pre-build research, development, and post-development, with factors such as effort, hourly rates, and compliance impacting the total. Fixed-price and Time and Materials models each have their pros and cons, suited for different project types and durations. Factors like scope of work, regulatory compliance, product design stage, and development approach (in-house vs. outsourced) play a crucial role. Strategies for cost optimisation include cross-platform tools, off-the-shelf code libraries, white-label solutions, design considerations, and best practices in DevOps.