Given their functionality, all smartphone brands are the same. Their similarities notwithstanding, they supply the same product at different prices in the same market. Strangely enough, the consumers do comply and willingly pay such price premiums. This study examines the mediation effect of price premium and brand preference on the causal impact of brand equity on sustainable purchase intention. The novelty of this study is in transforming the initial measures in a 5-point Likert scale into continuous values through a fuzzification and defuzzification process. Brand equity comprises three factors: brand awareness, perceived quality, and prestige value. Standardized questionnaire collected data in two countries (Taiwan and Indonesia) on two brands of smartphones (iPhone and HTC). Overall, 404 questionnaires were distributed in Taiwan, and 434 questionnaires were distributed in Indonesia. The data were analyzed by applying a structural equation model after conducting an exploratory and confirmatory factors analysis. In order to improve the estimations’ accuracy, the initial measures in a 5-point Likert scale were transformed into continuous values through a fuzzification and defuzzification process. The former consisted of assigning triangular fuzzy numbers, and the latter entailed assigning a center of gravity to each triangular fuzzy number and then extracting a random number from a normal distribution function based on the center of gravity. According to the results, price premium and brand preference exhibited significant mediation effects, with price premium having stronger effects than brand preference. Furthermore, the mediation effect was strongest for perceived quality and weakest for perceived prestige value.