The terms “vassalage” and “feudalism” as they are normally understood are inadequate to encompass dealings between men, and especially between members of the noble classes, as they are represented in the Cantar de mio Cid. Social relationships in the poem are marked by a moral and economic give-and-take that mirrors a particular state of society known as a “gift economy” in which exchanges of money and goods take place continually, but not under conditions that one would normally call “economic” in the modern world. The historian Georges Duby (1973), drawing upon concepts developed by the socio-anthropologist Marcel Mauss (tr. 1954), has interpreted the early economy of medieval Europe as one based on gift-giving. The model he proposes illuminates the meaning of gift-giving and other processes of the eleventh- and twelfth-century Castilian economy as they are found in the poem.

Through conquest and the income from various types of taxes, dues, and rents, nobles of the period were endowed with a quantity of wealth beyond what was needed for their daily sustenance, even granting that they clothed, fed, and equipped themselves on a scale above what was strictly necessary for carrying out the functions of daily life and of warfare. The economic workings of society required that such wealth be passed on to others. Generosity in distributing it was not simply an option open to the powerful: it was an obligation, albeit uncodified and often even unarticulated.