Pre-print, Working paper: This paper focuses on the role of age and age gaps in the mating process. We test the predictions of different theories of age heterogamy using a French exhaustive administrative database of newly formed same-sex and heterosexual couples. In both heterosexual and same-sex unions, age gaps and the likelihood of extreme age gaps increase with the income of the male richer partner, especially when he belongs to the top income decile. But women, even when they rank high in the income distribution, are usually matched with an older partner. Women are found to mate with a younger partner in only one specific case: above their 60s, when they provide at least 75% of the household income or rank higher than their partner in the distribution of income in their respective age group. The marriage market thus seems to be best described by exchange theory, mitigated by a remnant of patriarchal norms. In a way, the price of youth depends on the sex of the buyer.