You would need to know what to buy. Helium balloons...$1. Greeting cards, $.50, there are certain things that are much cheaper at Dollar Tree than else where. There are some items that they get you to splurge on impulse on that have a higher profit...Some candy you can get for $.70 at Walmart is $1 at Dollar Tree.
I have noticed that too. Some items are a good deal, some are average, and some overpriced relative to standard discount stores. Clearly Dollar Tree cuts the corner on materials and durability.
The items I am pleased are things like ceramic or glass dishes that are painted slightly imperfectly.