GaRam is a sales manager of an appliance store and she sometimes visit outlets run by competing stores. Six months ago, she noticed that rivals' prices were very close to the prices at her store. However, in the last six months, her competitors have lowered their prices to about 15 percent below the prices at her store. Nevertheless, the total unit sales at her store have increased slightly during this time period. Assuming rational buyers and no deceptive advertising, what is the rational explanation for this?