The storage cost on every transaction is due to the fact that every app you use has created smart contracts that require you to pay a fee for the use of that contract. This fee is called the gas fee and it is used to cover the cost of processing the transaction. Additionally, the storage fee is a โmaximumโ fee you are agreeing to pay up to that much storage, and it is often less than the maximum. For example, when minting Dummehs, the storage fee is only used to pay for the storage of the data associated with the transaction and is not used to cover any other costs. This fee is necessary to ensure that the app can continue to function properly and securely.