Abstract-Online merchants mistakenly tag ultra-low prices on their products or services from time to time. It is difficult to completely avoid such kind of mistakes that usually result in monetary loss and other negative consequences. Fortunately, pricing mistakes in online stores could be revealed through tracking shoppers' abnormal reactions. Thus, in order to disclose latent pricing mistakes within their storefronts, online merchants must learn how shoppers respond to these pricing mistakes. Due to the significance of the issue and the lack of corresponding resolutions, the present work conducted an empirical investigation of online shoppers' behavioural responses when they encounter ultra-low price tags. The research findings not just profile how general online shoppers would respond under the particular circumstance, the implications also induce a set of data indicators that can practically aid online merchants in disclosing those adverse mistakes promptly.Index Terms-online merchant, pricing mistake, price sensitivity, shopper's behavior.