It depends on what you are buying at Dollar Tree, some of the stuff can be purchased in bulk for cheaper at other stores (i.e. tuna, tomato paste, beans) but for things like cleaning products where there aren't greater gaps in quantity and quality between their stuff and their competitors (i.e. Bleach, Window Cleaner, Stationery) it makes sense to purchase from Dollar Tree.
This. If you do your due diligence it's not hard at all to save money at Dollar Tree. I haven't bought bleach from anywhere else in years. Name brand facial tissue is cheaper at Dollar Tree as well. It's not difficult to do price comparisons by unit price with your local supermarkets for identical goods to find out where the savings are.
Overall they're obviously price gouging and exploitative to lower income families, but it's not a universally shyt place to buy certain products. I've bought kitchen utensils, wrapping paper, baking soda, stationary items, greeting cards, hand soap, and plenty of other shyt from there recently that are far less expensive than grocery store prices per unit.
I can't remember the last time I bought any food items from there though. Agree that most of that shyt is straight garbage to consume.