The explicit assumption underlying Payments for Ecosystem Services (PES) is that offering payments that are at least equal to individual’s opportunity cost will act as a substitution within their global income. This acts under the more general hypothesis of money fungibility present in neoclassical economic premise. In the meantime, according to mental accounting theory, consumer track their financial activities using a set of cognitive labels depending to the context in which it was obtained, each of which being associated with a different marginal propensity to consume. In this work, we tested the effect of income’s framing (No effort based money vs. Effort based money) on spending decisions (Hedonic vs. Utilitarian) within Madagascar rural areas that are potential beneficiaries of PES programs, using a natural field experiment. As we shall see, the level of hedonic preferences is significantly higher in the ‘No effort’ condition. Our results demonstrate that mental accounting matters in a natural field context and could bias environmental conservation policies. Enlarging the initial focus of our investigations, this work leads us to a wider discussion on moral accounting, suggesting effects applying to both financial and moral spheres.