It's a definition that works for how economists talk about things, but is extremely out of phase with the colloquial definition. Hence the stated outrage from t

It's a definition that works for how economists talk about things, but is extremely out of phase with the colloquial definition. Hence the stated outrage from the parent on how the poor spend so much of their income on "luxuries", when that refers to different things than what most non-economists would define as "luxuries".