The Bitcoin mining pool with the highest total hash rate, Foundry USA Pool, has refunded an accidentally paid Bitcoin transaction fee, worth approximately $777,000 (8.18 BTC). On December 19, Foundry USA Pool mined Bitcoin block 875475, which included a transaction where the sender attached a fee of 8.18 BTC, 91,127 times higher than the necessary fee. On Friday, Foundry posted on social media that it had contacted the sender who 'accidentally' paid the fee. The mining pool confirmed that it had refunded the transaction fee to the sender 'after careful consideration'; otherwise, the fee would have been allocated to mining clients contributing hash power to the Foundry pool.