Your yearly Costco spending is rather reasonable so long as you're actually consuming the food before it goes bad.
When I lived alone, my strategy for shopping at Costco was to skip the cart, except for the yearly acquisition of toilet paper and other bulky but non-perishable items. Really made me think about what I was picking up and if I'd actually consume it all. Nowadays, our household uses Costco to buy sardines, canned tuna/salmon, frozen salmon, nuts, frozen fruits, coconut oil, avocado oil, and Kerrygold butter. On those items Costco prices and quality can't be beat--as the Real Food Shopping Guide of Costco suggests. Most of our regular grocery shopping is done at an international grocery (best prices on immensely varied produce, spices, and fresh fish), while the chicken, beef, and dairy we get delivered weekly from a farm. Breads come from a bakery within walking distance, but that's like three loaves a month (two of which are for a monthly meeting we host). When the farmer's market nearby is seasonally open, my DW likes to spend lots there on tomatoes, peaches, apples, and okra. I'd complain with how much she can spend, except for the fact that she's home all day without a car and she enjoys the regular Wednesday walk up there with our son, plus the produce tastes amazing as long as you can eat it before it spoils. Spend your money on groceries to help avoid spending it on restaurants. As we've become better cooks we have less and less of an interest in eating at restaurants, and have been much more capable of using the food we have on hand.