I purchased an item for R1. I have the right to sell this item for R1, R10, R20, R50 or at any other price. There is no sin in this. However, if the transaction was settled in a way that the buyer says: “Make a profit of 10c on the item and sell it to me”, and you say: “Okay, I will sell it to you after making a profit of 10c on it”, then in such a case it is not permissible for you to make a profit of more than 10c on that item. Alternatively, the buyer says: “For whatever price you purchased it, add 40c profit to it and sell it to me.” Even in such a case, it will be wajib on you to quote the correct price and it will be haraam to make more than 40c profit. Similarly, if you tell the buyer: “I will sell this to you at cost and I won’t make any profit from you”, it will not be permissible to make any profit. It will be wajib to quote the cost price.
You intend purchasing an item and you ask the seller to sell it to you at a profit of 10c. He replies: “Okay, I sell it to you at a profit of 10c.” Alternatively, you say: “Sell it to me at your cost price.” He replies: “Okay, give me that amount and don’t give me any profit.” However, in both cases, he did not tell you the cost price of the item as yet. In such a case, if he quotes you his cost price before getting up from his place, the transaction will be valid. But if he does not quote you the price at that place, and says: “Take the item now, I will check the price and inform you” or says something else, then in such a case the transaction will be fasid.
After taking the item, the buyer learns that the person hadn’t quoted the correct cost price and had made a profit more than what he had promised. In such a case the buyer does not have the right to give a lesser amount. If he wishes to purchase the item, he will have to pay the price that was quoted to him. However, he does have the right to return the item if he does not wish to purchase it. If the seller had agreed to sell the item at cost and had promised that he will not make any profit and thereafter quoted an amount that is more than his cost price, then he does not have the right to take more than the cost price. The buyer has the right to pay the cost price and not pay the additional amount that he had quoted.