In the wake of the COVID-19 pandemic, a significant shift in consumer behavior has accelerated the transition towards e-commerce, with a notable surge in online group buying. This research pioneers the integration of the Theory of Planned Behavior with neurophysiological measurements to dissect the complex interplay between product price, risk perception, and consumer trust in influencers on online group buying intentions amidst a global health crisis. Unlike previous studies that primarily rely on self-reported data, this investigation employs brainwave analysis to capture the immediate physiological responses of consumers to pandemic-related stimuli, thereby offering a novel perspective on the underlying psychological processes. Our findings reveal that while traditional factors such as price, quantity, and time continue to influence purchasing attitudes, the pandemic has uniquely modulated these effects, with social influence playing a pivotal role in shaping trust towards influencers and, consequently, group buying intentions. Significantly, the study uncovers that COVID-19's impact, though seemingly negligible in survey responses, exerts a profound influence when assessed through experimental measures. By bridging the gap between theoretical models and empirical neurological evidence, this study not only addresses a critical research void but also enhances our understanding of consumer decision-making in times of uncertainty. This advancement in knowledge contributes to the extant literature by providing a more nuanced and comprehensive analysis of the factors affecting online group buying, offering valuable insights for both academics and practitioners navigating the evolving landscape of e-commerce during and beyond the pandemic era.