When you are seeking out customers for your business you need to stand out in some way. One way to do this is to offer a lower price. Many smaller startups can offer lower prices because their overhead is lower. As you are in business longer, there is a tendency to gradually raise prices due to many factors. The first being that you can because your customers are more comfortable with your service/product and will pay more for a known quantity.
When Home Depot enters into a new area, they lower prices which tend to knock out other stores in the area, in a similar business. Then when there is less competition, they raise profits because they can and because they know with less competition consumers have less of a choice.