When buying an NFT, you pay for storage fees as part of the transaction. This is because any time you call a contract, you have to pay for the additional storage used during that call. This is to ensure that your transaction is successful and that you don't experience any errors. After the transaction is confirmed, you can check the actual storage cost you paid, which is often much lower than the maximum storage cost that was estimated. When you sell an NFT, you also have to pay for storage fees, as the transaction will use additional storage. This is a necessary cost of doing business when dealing with NFTs, as it helps to ensure that the transaction is secure and successful.