I often get questions on what's considered a good buy. One way to tell is by checking out the shopping list for the week at your favorite store on Grocery Smarts website. Anything that is a 5 star item is definatley something you want to stock up on (assuming it's something you'll use). A 4 star item is still pretty good and a 3 star item is an okay deal. I would not encourage you to buy anything that is a 2 or 1 star item (they rarely make the list anyway).
I also came across another list on Google that is a reference list. I'm not sure who the original publisher of the list was, but as far as I can tell these prices are pretty consistent with what I've been seeing.
5 star - stock up
4 star - still a pretty good deal (stock up with a few if you absolutely need it)
3 star - average price
Hip2Save’s Daily Recap of Deals (4/26/2017)
3 hours ago