What contrasts emerge from Chapter 12?John Steinbeck's The Grapes of Wrath

Chapter 12 is one of the intercalary chapters in
Grapes of Wrath that imitates techniques used previously by John
dos Passos in his USA Trilogy, techniques which included a newsreel
and a camera's eye recounting of historical incidents that occurred in the historical
setting common to both novels. 

In much the style of the
old reporters from the newsreels at the movie houses, Route 66 is described as the main
migrant road, the mother road to which rutted country roads and tributary side roads
connect.  In the 1930s before any interstate highways, Route 66 ran across the country,
transporting victims of the Dust Bowl from Oklahoma to California.  However, along the
way, through the desert and over the hills, these transitory people experienced the
anxiety of never knowing if their old vehicles would make it to the new frontier.  They
worried about old tires, rattles, broken fan belts.  They faced hostility:  "Whyn't you
go back where you come from?"  They encounter unethical salesmen who raise prices for
old tires because they know people are desperate:

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Fella in business got to lie an' cheat, but he
calls it somepin else.  That's what's important.  You go steal that tire an' you're a
thief, but he tied to steal your four dollars for a busted tire.  They call that sound
business.

Clearly, here
Steinbeck satirizes capitalism that condones conduct that is contrary to moral laws.  At
the same time, however, he praises the sense of the fraternity of man as the narrator
relates a story of a family who had no vehicle, but put all their belongings on a
homemade trailer:

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They pulled it to the side of 66 and waited. 
And pretty soon a sedan picked them up.  Five of them roade in the sedan and seven on
the trailer, and a dog on the trailer.  They got to California in two jumps.  The man
who pulled them fed them.  And that true.  But how can such courage be, and such faith
in their own species? 

The
paradox of these migrant families is expressed in the final
paragraph, 

The people in flight from the terror
behind--strange things happen to them, some bitterly cruel and some so beautiful that
the faith is refired forever.