Due to the development of e-commerce, customers are rapidly shifting from passive receivers of information to content contributors. Two types of content coexist on modern e-commerce platforms like Amazon.com, called seller-created and buyer-created content. Extant literature suggests a range of factors that influence product sales on e-commerce platforms, including informativeness, readability, multimedia richness, and extreme valence. However, interactions among the mentioned factors from both seller-created and buyer-created content remain to be empirically verified. This research embeds dual processing theory and dual coding theory as theoretical foundations in the conceptual framework, which determines the interrelationships among key drivers that affect product sales. To verify the hypotheses, we collected the data from Amazon (n = 5248) and estimated the empirical model using partial least squares structural equation modelling (PLS-SEM). Among the results, it is highlighted that review informativeness fully mediated the influence of product description informativeness on product sales. While readability, multimedia richness, and extreme valence from buyer-created content exert both direct and moderating effects, the only factor from seller-created content that significantly affects product sales is multimedia richness. These findings confirm that, with the presence of customer reviews on product pages, sellers are losing control over the relevant information on their brands and products on the e-commerce platform: factors from buyer-created content are more directly influencing product sales. Nevertheless, sellers can still influence product sales by enhancing their content's informativeness and media richness.