There's a video at Dollar Store Crafts that says that you should
- "check the price tag (not all dollar stores sell EVERYTHING for $1)
- avoid toothpaste as a lot of counterfeit toothpaste finds its way into dollar stores (and it can even be harmful)
- avoid medicines and vitamins (some are close to expiration or do not contain the ingredients they are supposed to)
- watch out for some children's toys (can be choking hazards or contain lead)"
This is common sense but bears repeating. You'd have the same issues at a swap meet or second hand store or off-price outlet; it just pays to be a wary shopper and read labels.
I walked through a dollar store today, and there wasn't much to write home about. Most of it looks like it's trying to imitate the real thing, brand wise, or is cheaply made and not worth the money, even at only a dollar a pop. I don't fancy supporting China's monolithic manufacturing, either; most things are made in China.
I've read that people have found lots of things for preps at dollar stores; maybe it's just me and we are well prepared enough now that I don't feel compelled to buy, or maybe I'm too leery of buying off-brand items at a dollar store, but I don't think I'd buy much for preparedness there.