Motif- "One Man's trash, is another man's treasure"

Barbara Kingsolver simplifies the motif/adage of “one man’s trash, is another man’s treasure” in The Tortilla Curtain best when she says, “He (T.C. Boyle) comically and painfully details the smug wastefulness of the haves and the vile misery of the have-nots.” In the novel, Boyle constantly reminds his audience that the simple necessities, the “trash” Delaney (a symbol of the typical American, myself included) takes for granted such as hot running water, a fridge full of food, and a roof over his head are the “treasures” Candido (a symbol of the border-hopping-American-dream-seeker) strains for as he heaves himself up the trail from his shanty shack, day after day, in search of work.
Why does Boyle keep Candido in a constant state of misery? Why does he get Candido’s hopes up and then crush them so vehemently? I believe this is because Boyle wants his readers to appreciate the abundance of which we, the American public, fail to recognize in our everyday lives. He repudiates this idea in the text when Candido feels “as happy as he had ever been (Boyle257),” while roasting a small turkey, a thanksgiving gift from a benevolent citizen, without the fixings for thanksgiving. Because even without the mashed potatoes, the turkey gravy, the cranberries, etc. Candido is grateful for his blessings, however small. This is the moral lesson that develops throughout the novel, that the simplicity of one’s life and the contentment one has for their life is the key to happiness.