The largest Bitcoin mining pool, Foundry USA Pool, has refunded an unintentional Bitcoin transaction fee worth approximately $777,000 (8.18 BTC). On December 19, Foundry USA Pool mined Bitcoin block 875,475, which included a transaction in which the sender attached a fee of 8.18 BTC, which was 91,127 times higher than the necessary fee. In a social media post on Friday, Foundry said it had contacted the sender who had "inadvertently" paid the fee. The mining pool confirmed that it had returned the transaction fee to the sender "after careful consideration", otherwise the fee would be distributed to the mining customers who contributed to the Foundry pool's computing power.