Tactile sensing is essential for safe and effective human–robot interaction, particularly in industrial and service robotics. While numerous tactile sensor arrays based on piezoelectric, piezoresistive, and capacitive mechanisms have been developed, most suffer from complex structures, high material costs, and sensitivity to environmental factors. Here, we present an entirely soft and stretchable binary tactile sensor array based on a mechanical switch structure. The design enables stable, robust contact detection using only passive structures and low-cost materials. A 6 × 6 sensor array is demonstrated, achieving accurate touch detection with high robustness, signal stability, and scalability. The total material cost per sensor is below 1 USD, highlighting its potential for widespread deployment in cost-sensitive robotic systems and consumer electronics.