LOL. There is the theoretical option of marrying without sending kids to college (or having kids in the first place) or buying a house. Also an option to have kids or buy a house without getting married. And as far as groceries are concerned I would have assumed that a two (or three or whathaveyou) person household spends less per person on that than a single household - economies of scale, etc. Travelling alone definitely is more expensive per person than travelling as a couple as hotels charge extra for the unused bed and since when do married people dress better than singles?????
Maybe a Sensor-type can answer this question if they have an accounting degree?