This study analyzes the value addition of Agile, Waterfall, and Hybrid software development models at various stages of the software development lifecycle (SDLC). By examining how these models impact cost estimation accuracy, the research aims to determine the efficiency and effectiveness of different methodologies. The study employs quantitative analysis, expert surveys, and case studies to evaluate cost fluctuations, project success rates, and stakeholder satisfaction. Findings provide insights into how each model enhances value and contributes to overall project sustainability.