Contingency approaches for understanding complexity in projects are intended to help academics andpractitioners make distinctions between different types of projects to better understand the relationship betweenpractices and outcomes when applying different project management processes. In this paper, we build onexisting research on complex products and systems (CoPS) to address the challenges of managing costs inprojects of varying complexity. Based on a qualitative case study, we identify several challenges in performingvarious cost management functions related to cost estimation, cost control and monitoring, revenue recognition,profitability analysis and margin calculation. The cost management functions are impacted by the large size,complexity, uncertainty and uniqueness of those projects.