Praise be to Allah.
What you should do is not increase the value of the item to more than its market value. There is nothing wrong with lowering the price and making it less than the market value for some customers; rather what is forbidden is increasing it and making it higher than the market value for some customers, especially if the purchaser is unaware of market prices or he is inexperienced in buying and selling and bargaining. It is not permissible to take advantage of his ignorance and inexperience and charge him a price higher than the market value. End quote.