The best way to introduce higher priced merchandise in a store that is not known for such merchandise is to draw on the store’s existing reputation and then to try to use that reputation to convince people to buy the higher priced new merchandise.
Let us imagine that you have a store that has been a fixture for people who want moderately priced merchandise. People have come to trust you to give them quality for their dollar. That is a sort of brand equity on which you can build. You can tell people things like “Even higher quality from the store that gives you value for your money.” By launching an ad campaign like this (hopefully with more polished slogans), you can leverage the reputation that you already have. It will also help if the higher priced merchandise is from the same brands that you have already been selling. That, too, allows you to play up the idea of continuity. In such a case, you can sell people by emphasizing that it is the same producer and the same retailer, just with a new level of higher-quality goods.