A subjective well-being approach is followed to assess the magnitude of inefficiency in the use of income. The approach has the advantage of relying on people’s reported well-being outcome: their economic satisfaction. In this sense, the approach does not impose top-down nor normative criteria in judging the use of income; on the contrary, the approach assesses the existence of inefficiency based on people’s own assessments of their well-being situation, given their own personality and cultural traits. The information comes from a Mexican survey, and an X-inefficiency thick-frontier technique is used. The paper shows that there exists substantial inefficiency in the use of income at all income levels, even for those in income poverty. It is shown that inefficiency is significantly related to practices, attitudes, and motivations for consuming; some of these aspects may be context dependent, reflecting social trends that induce specific consumption patterns. Economic theory has focused on rising people’s income to increase their economic well-being; this paper shows that reducing inefficiency in the use of income is an alternative instrument that deserves further consideration.