I check all three places and pay attention to coupons frequency at my grocery store, too. I keep a tally of what price per oz is and compare across each place. Beef is cheaper at my grocery store, chicken cheaper in bulk at sams, Baby formula cheaper at Amazon, coffee I buy at my grocery but like 6-8 bags (small bags but sealed) when the coupon comes up every three months (partly based on taste here). Etc. I have frequently found that sometimes sams or Amazon are more expensive than my grocery store. Sometimes based on sales my grocery does occasionally, sometimes just randomly cheaper. I use the apps on my phone to shop around (HEB app + curbside is the bomb even if they do charge 3% more to use it, I'll gladly pay 10$ to save an hour of my time) I've heard Aldi is worth checking out too, we don't have one around here so idk. Some items I'm learning to make from scratch since it's cheaper to just buy base items. Things like pasta, spaghetti sauce, cheese sauce, bread, spice mixes, cream of whatever soups, etc. Haven't gotten into crackers, cereal/granola or chips yet but those are on the list to try.