Cost–Benefit Evaluation in Sustainable E-Commerce: Associations of eWOM with Purchase Intention and Self-Reported Expenditure

Sustainable e-commerce has become increasingly relevant, although the mechanisms through which online reviews are associated with purchase intention and consumers’ economic engagement require more precise explanation. This study examines a cross-sectional model in which positive and negative eWOM are associated with the cost–benefit assessment of sustainable online purchasing, and this assessment is related to purchase intention and the level of self-reported annual expenditure. The proposed model integrates Signalling Theory and Social Exchange Theory. Covariance-based structural equation modelling was used to analyse data from 520 consumers in Extremadura (Spain) with prior experience of sustainable online purchasing. Positive eWOM was associated with greater perceived benefits, while negative eWOM was associated with greater perceived costs. Benefits were positively related to intention, whereas costs were negatively related to it. Intention showed a positive association with higher expenditure categories, which was additionally tested using ordinal logistic regression. The findings show how eWOM valence is linked to distinct components of exchange assessment. Given the cross-sectional and self-reported nature of the data, the relationships should not be interpreted as causal or as a temporal conversion of current intention into expenditure reported for the preceding twelve months.