I love the Costco Tillamook cheddar and my girlfriend loves the whipped cream we get from there. I used to drink 2-4 cups of whole milk / day when paying off my student loans and bulking but it seemed to affect my stomach poorly. So I switched to almond milk for my protein shakes.

Some of my favorite ways to make tasty chicken + rice dishes from Costco is the Maya Kaimal simmer sauce the frozen stir fry vegetable mix. The simmer sauce isn't the cheapest option, but I pay extra to make my normally boring/cheap food taste good enough to eat for 5+ days straight. I use my pressure cooker and end up with super tasty Indian meals without the chicken being overcooked.

Kirkland Signature unsalted mixed nuts are also a lifesaver and a part of my daily breakfast. Decent calories / dollar (400 ish depending on the price) but great nutrition density.