Anyone shoping only at Costco for family groceries and able to save money?

tl'dr - We're trying to save money at the grocery store. Publix has gotten outrageous. Trader Joe's saved us a ton of money but the boxed stuff was shite and about 20% of the produce spoiled before the end of the week. Would like to only go to Costco to save money but don't want to waste time. Anyone having luck with them as their sole grocery store? Maybe Walmart on the side for non-perishables?

We noticed that our grocery bill has skyrocketed over the past 6 months. Almost a year ago, I posted about the possibility of lowering our monthly grocery bill to $500/month and still eating healthy. You can read the thread here if you want. Summary is that the answer was obviously no.

I don't even want to admit how much we've been spending since around November. It's way too damn much.

I went to Trader Joe's last week to see if I could save money, and I did. A lot! Our ~$250/week Publix bill (not to mention eating out, Costco, and a few random Target runs for necessities) was $80 at Trader Joe's and $60 at Costco. The Costco foods are lasting us two weeks, so I would say last week's grocery bill was really ~$110 for the entire week. We made the effort to not go back to the store and only ate at a restaurant once the entire week, so the total for our 7 days of eating was about $160. Say realistically we spend $200/month on food and necessities for ~800/month for a family of four. That's a huge amount of savings.

Publix's ridiculous prices were confirmed yesterday when I stopped to grab baby food, a few items for a Mother's Day dinner (for six), and a few needs for the house. It was $120. $110 at TJ and Costco lasted a week. $120 at Publix was one meal and bananas, milk, eggs, and baby food. The meal wasn't ritzy gourmet by any means.

Problem at Trader Joe's though was that the food quality was mostly bad. My son had never had Cinnamon Toast Crunch before, and we picked up the TJ brand. It was cardboard with some cinnamon flavor. The two onions we got from there were rotten in the middle 5 days after purchase. Two of the avocados were somehow moldy just as they ripened.

Costco foods always seem to last a while, but buying vegetables and fruits in that kind of bulk seems like it could become a waste too. Not sure I'll go through a box of onions before they rot; nevertheless, I'm certain that I'll get through two of them in a week without them rotting in the middle. There's also the worry that we'll get sick of 100 of the same granola bars (or whatever) before we finish them.

frick this has become an Oweo journal entry. Just read the tl'dr.