The Blue Cash card from American Express gives you 5% back for purchases at supermarkets, gasoline stations and pharmacies once you've spent $6,500 on the card. For purchases at Costco, you get 1.5% back. All other purchases give you 1.5% back, not the usual 1%.
The True Earnings card, which is also a Costco card, gives you 3% back on restaurant meals, 2% on hotels and rental cars, and 1% everywhere else, including Costco. If you are an executive member at Costco ($100 annual fee), you'll get another 2% back from the warehouse store. Yesterday, I received $167.66 from Costco. Bon apetit!
(The original post described the second card incorrectly as the True Value card.)