Praise be to Allah.
Ruling on selling items with a detailed description
It is permissible to sell items with a detailed description that will not lead to any dispute. Then if the item turns out to be different from the description, the purchaser has the option to return the item, or keep it without compensation, meaning that he does not receive any compensation for the discrepancy. This option is referred to as the option to cancel the sale when there is a dispute about the description of the item.
If the item turns out to be defective or damaged, even slightly, but the damage affects its value, then this is a defect, and the purchaser has the option to cancel the deal in the case of defects. So he has the choice between returning the item or keeping it and receiving compensation for the defect.
It says in Kashshaaf al-Qinaa‘ (3/218): Chapter on one who purchases a defective product and was unaware of the defect at the time of the sale, then he found out about the defect. He has the option [of cancelling the deal], regardless of whether the seller was aware of the defect and concealed it from the purchaser, or he was not aware of the defect. … and the purchaser has the option of returning the item and taking back his money without incurring any loss, and avoiding any loss that he could have incurred if the item had remained in his possession with a value lower than the price that he paid for it. If the purchaser chooses to return the item, then he is responsible for returning it to the seller, because of the hadith which says that a person is responsible for what he takes until he gives it back.
When he returns it, he may take back the price in full, because by annulling the deal the purchaser is entitled to receive his money in full. … Or he may keep the item and receive compensation for the defect, if it is not possible to return the item, whether the seller is happy to give him compensation or not.
Returning the item when there is a defect or damage
When there is damage or a defect, you have the right to complain about the vendor so that you will be able to return the item and get your money back, or keep the item and receive some compensation for the defect [such as a reduction in the price].
You do not have to worry about the fact that if you register a complaint the vendor may not take the item back, because that will cost him more money. This is up to the vendor: if he wishes, he may let you keep the product, or if he wishes, he may take it back.
Even though the cost of returning the faulty products should be borne by the purchaser, if the rules of selling on eBay dictate that the cost of returns should be borne by the vendor, there is nothing wrong with that. It is like a permissible condition in buying and selling, if both parties are aware of it at the time of the transaction.
But you must make sure that you are accurate and truthful when informing the seller of the defect or damage affecting the product. If the seller returns the money to you, and does not ask you to return the item, there is nothing wrong with you making use of it, because it is an item that the owner no longer wants.
And Allah knows best.