This paper provides an analysis of firms’ optimal prices when individual utility exhibits both material and other consumer effects. We construct a model and conduct an analysis in the following four steps: (1) By using a conjoint analysis of data, we set up a hierarchical Bayesian model and estimate its parameters, which are composed of individual utility functions. (2) We calculate the number of sales in each time period and derive the total sales throughout the given period. (3) We estimate the demand functions in the presence and absence of consumption externalities. (4) Finally, we calculate the profit functions and derive the optimal prices taking into account various product attributes. By applying our analysis to the book market of Japan, we find that the optimal price is lower when an externality is present than when absent. The intuition behind this result is that pricing low and selling a large number of books from an early stage increases the externality effect, yielding a higher profit for firms.