The prices listed first here are those at the Waltham, Massachusetts, Costco; the prices in parentheses are for an equivalent amount (often consisting of several individual packages) at nearby markets.

Basmati rice $9.99 for a 20-pound sack ($29.80).
Dried shiitake mushrooms $9.99 per pound ($95.36).
Extra-virgin olive oil $9.49 for 3 liters ($14.99).
Filet mignon $8.59 per pound ($21.00).
Frenched lamb roast $7.99 per pound ($15.99).
Medjool dates $6.99 for 2 pounds ($9.96).
Sliced smoked salmon $10.99 per pound ($16.00).
Sun-dried tomatoes $7.69 for 2 pounds ($50.94).
Veuve Clicquot Brut Champagne, nv $28.99 per bottle ($39.99).
Whole cooked dungeness crabs $3.99 per pound ($5.00).