Is a graphics card's specifications differing considered a defect that permits returning a used device, and is the seller entitled to take a sum of money for the return after four days of purchase?

If the device does not match the described specification, you have the option to return it without paying compensation, or to accept it and claim compensation for the defect (arsh al-ayb), or to be content with it. The seller is not permitted to compel you to pay a sum for returning the sale, because he deceived you by mentioning untrue specifications. The buyer has the right to annul the sale if he discovers a defect of which he was unaware, and he has the right to a full refund of the price. Using the device before discovering the defect does not obligate you to anything. However, using it after discovering the defect is considered acceptance and forfeits the right to annulment. In this case, if the device is returned, it is considered a rescission (iqalah), and the seller may request compensation. Paying a sum to maintain goodwill and companionship is not considered extravagance.