In The Great Gatsby, how does the conspicuous consumption of those living in West Egg contrast with the poverty represented by the Valley of Ashes?

This is an excellent question that recognises how setting
is used symbolically in this wonderful novel. Of course, the Valley of Ashes is
described very symbolically to represent a place barren of hope. It is no mistake that
this is the home of the Wilsons, who try to get ahead in life yet seemed to be doomed to
living on a low social level. Consider how the Valley of Ashes is described in Chapter
Two:

This is a valley of ashes--a fantastic farm where
ashes grow like wheat into ridges and hills and grotesque gardens; where ashhes take the
forms of houses and chimneys and rising smoke and, finally, with a transcendent effort,
of men who move dimly and already crumbling through powdery
air.

The
metaphor of describing this location as a "fantastic farm" which grows ashes clearly
says a lot about the reality of life in this industrial zone, and we can see through the
description of George Wilson, who is a thin, pale man, somehow faded, that he is a
suitable citizen of this part of
town.

However, let us compare
this with the way that Gatsby's parties are described at the beginning of Chapter
Three:

There
was music from my neighbour's house through the summer nights. In his blue gardens men
and girls came and went like moths among the whisperings and the champagne and stars. At
high tide in the afternoon I watched his guests diving from the tower of his raft, or
taking the sun on the hot sand of his beach while his two motor-boats slit the waters of
the Sound, drawing aquaplanes over cataracts of
foam.

Note how wealth and its
decadent display are emphasised in such passages. Firstly there is a lot of colour in
this passage, compared to the grey of the valley of ashes. Likewise, almost every
sentence contains the trappings of wealth, whether it be with references to champagne,
motor boats or other things.

Thus we can see the way that
West Egg functions symbolically to represent the home of new wealth, with all of its
garrulous overtness, and the Valley of Ashes represents the hopelessness of industrial
areas.