Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Mocking, Hilarious, Philosophic
"The Diamond as Big as the Ritz" is definitely satirical (see "Genre"), so we expect a certain sarcastic bent to the tone. And that's exactly what we get. Fitzgerald parodies the Washingtons' indifference to the suffering of others and their willingness to sacrifice others for their own success. He does so indirectly. While saying with words that this behavior is perfectly natural, he says with his tone that it's clearly not. Example:
[Fitz-Norman Washington] was compelled, due to a series of unfortunate complications, to murder his brother, whose unfortunate habit of drinking himself into an indiscreet stupor had several times endangered their safety. But very few other murders stained these happy years of progress and expansion. (4.11)
Humor aside, Fitzgerald is still Fitzgerald, and he can't help but insert a gem or two of philosophic gold, not to mix our diamond-encrusted metaphors. He manages to sneak in a few comments here and there. He says, for example, that youth is nothing but chemical madness, that one can not be both free and poor, that the young live in the future rather than the present. And we're betting you can find a few more.