This study investigates the impact of solar and wind-based energy capacity expansion on electricity market prices and cost structures in Türkiye from 2020 to 2024. The rapid integration of renewable energy resources has significantly transformed Türkiye's electricity market, a key example due to the country’s ambitious renewable energy goals. Using high-frequency data from the Turkish Electricity Market (EPİAŞ) and applying econometric methods such as time-series analysis and regression techniques, we demonstrate that the substantial growth in renewable energy capacity has resulted in a pronounced "duck curve" effect. This has led to significant midday price reductions, with solar based energy generation increasing over tenfold, contributing to a 20% drop in midday prices. Wind energy, though variable, also contributed to lower marginal prices during periods of high generation. Despite these benefits, the intermittency of renewable resources remains a challenge, highlighting the continued need for conventional energy resources such as imported coal and natural gas for grid stability. Market interventions, including price caps and renewable energy support mechanisms (YEKDEM), have mitigated extreme price volatility. However, they emphasize the need for improved grid flexibility, energy storage solutions, and more accurate forecasting. This study provides empirical evidence of the duck curve effect in Türkiye's electricity market, offering policy recommendations for optimizing renewable energy integration, enhancing forecasting precision, and reducing system costs. Our findings emphasize the dual role of renewables in driving price reductions while posing challenges for grid management, underscoring the importance of innovative market mechanisms and technological advancements for a sustainable energy transition.