I live close to an aluminum factory. We also have a brewery. The retailers dare not raise prices anyhiw. They keep the markup minimal because we can easily switch to buying from the factory easily.
Generally, cities that have factories for particular products always sell that product cheaper. Cost of transportation for goods to other cities is one of those things that raise prices of products.
Shopping from the factory is what I try to do as much as possible. Anything that is produced around me, I try as much as possible to buy directly from the producer.