Sad faces and Balthazar's golden ship in Pieter Bruegel the Elder's “Adoration of the Magi”

In Pieter Bruegel the Elder's "Adoration of the Magi" everyone looks thoroughly miserable, though the occasion is, broadly speaking, a happy one: the birth of a saviour. And then there is Balthazar, the only guest who has brought a decent present: a golden ship with a nautilus shell of rare beauty inside. I quite understand the feelings of the Holy Family; I, too, am usually given all sorts of rubbish