The article explores how two companies compete by offering a service with two prices: a fee and a rate. If one company sets its fee or rate significantly lower than the other, both can make profits. This creates a kind of product difference even though the service is the same. Customers who use the service a lot tend to choose the lower rate company, while those who use it less go for the lower fee company. When prices can't go negative, competition is less intense, leading to higher profits overall. But if one company starts with a higher fee than the other, it's at a disadvantage.