In project management, the conventional focus on time and cost often overshadows quality’s undervalued, yet pivotal role. This study explores the nuanced dimensions of project success, centering on the Iron Triangle components: time, cost and quality (TCQ). Although quality is acknowledged in theoretical definitions, its economic significance and precise impact remain underexplored. This research addresses this gap by scrutinising the interplay between traditional success factors and project economic outcomes. By comparing projects with and without economic benefits, the study examines potential variations in TCQ influence. Furthermore, the research identifies specific traditional success factors associated with economic benefits and probes for a dominant factor with superior impact. A novel Project Unified Index (PUI) is introduced, enabling comprehensive economic performance assessment through TCQ analysis and statistical techniques. Intriguingly, the exploratory analysis reveals that time and quality possess more significant influence despite the apparent correlation between cost and profit. Quality emerges as a potential determinant, its significance often masked by meticulous measurement. This study underscores the paramount importance of quality, necessitating its redefinition across industries in a customer-centric manner. By repositioning quality as a decisive factor, this research reshapes perspectives on project management, steering future investigations towards a comprehensive understanding of quality’s pivotal role. The data for analysis were collected with the participation of a prominent professional project management association and a business master’s program in Hungary.