This paper provides modeling-based insights into price formation and strategic interactions in the global solar PV supply chain. It analyzes how market outcomes differ when dominant exporting and importing regions behave strategically rather than under perfect competition. An Equilibrium Problem with Equilibrium Constraints (EPEC) framework tailored to the global solar PV supply chain is developed, enabling the endogenous determination of regional market-clearing prices un- der strategic interaction among multiple geographically distinct regions over the period 2025–2040. To solve the resulting model, an enhanced Gauss–Seidel diagonalization approach is proposed that jointly integrates damping and proximal regularization within an adaptive tightening scheme to improve convergence robustness under strong strategic coupling and long-term in- vestment decisions. The results indicate that, under strategic behavior, market-clearing prices in the European Union (EU) and the United States (US) remain substantially above the global welfare-maximization benchmark. Under purely economic incen- tives, dominant exporters initially undercut regional production costs to gain market share, contributing to the exit of domestic manufacturing capacity in the EU and US. The model further highlights persistent excess capacity as a structural feature of strategic competition, suggesting that overcapacity can act as a strategic buffer in global supply chains.