My cup overflows
Luxury as a word that came from the idea of abundance or plenty. My cup overflows was written by a man who had few possessions, for as a nomadic herdsman he could carry only necessities.
This cup phrase is used to illustrate more than his current fluid intake, it could indicate a life of luxury, a personal world of abundance. Material plenty also removes worry about the future.
This poem we call Psalm 23 is not about material things, it is about a spiritual realm. As human beings we have free access to the spiritual and crave satisfaction.
Presented to us here is a flow of deep satisfaction and joy that fits our internal need. The whole psalm is about harmony with God and the peace that follows. This is real luxury.