In the US, so-called ‘Dollar stores’ are ubiquitous. There are two very close to where I live. These stores offer all manner of items, food and household goods, priced at around a dollar, so that makes it cheap to shop. As far as I can tell, their model is to buy large stocks of items that manufacturers want to offload at hugely discounted prices for whatever reason and then resell them. This means that what you find in the stores is highly variable from day to day, depending on what items manufacturers were clearing out. You just have to try your luck.
In the latest episode of his show Last Week Tonight, John Oliver says that the business model of these companies is to make profits by understaffing its stores and underpaying its employees. While these stores are sometimes the only retail outlets in poorer neighborhoods and thus seem to serve a need, another problem (that Oliver did not address) is that by using their size to get huge quantities of stuff at low prices, they often drive existing mom-and-pop stores in those neighborhoods out of business. Thus the need they are serving is one that they helped create.