That's called a loss-leader strategy.
It's the same strategy fishermen use when they invest a small amount of money at the bait store before a fishing trip. As you said, it's a lure.
The strategy is not exclusive to dollar stores.
> Like other retailers, a dollar store's interior layout is set up so that commonly purchased staples like cleaning supplies and milk are in the back of the store. This requires shoppers to walk through other aisles, resulting in impulse buys.
So, people's thoughts and decisions are affected by what is immediately in front of their eyes, despite their considered intentions arrived at through deliberation.
We all know that's true because it happens to us, and we've all experienced forgetting something until we walk out of the house, and then returning to inside the house or room before we can remember it again. Our thoughts are significantly dependent upon our circumstances.
What's surprising is that the full impact of our non-independence of thought has not been well accounted for by philosophers who speculate about the concept of free will.