Despite growing regulatory concerns about potential overcharging of sustainable investors, empirical evidence is lacking. In two controlled laboratory-in-the-field experiments with 415 professional financial advisors from Europe and the United States and an incentivized survey, we identify two distinct but interacting effects. First, advisors charge sustainable investors a premium. This premium persists even when accounting for differences in skill, effort, and costs. Second, advisors impose higher fees on clients with low financial literacy. These factors interact. Sustainable investors with low financial literacy are charged the highest fee, whereas those with high financial literacy do not pay a sustainability premium. Our findings suggest that advisors extract additional fees for sustainable investment mandates but avoid overcharging sustainable investors with high financial literacy. This paper was accepted by Camelia Kuhnen, finance. Funding: P. Smeets was supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek Grant VI.Vidi.221E.011. The experiments were financially supported by the Graduate School of Business and Economics at Maastricht University, Vrije Universiteit Amsterdam, and Radboud University. Supplemental Material: The online appendix and data files are available at https://doi.org/10.1287/mnsc.2025.00232 .
Laudi et al. (2026) studied this question.