A crypto exchange accidentally paid a $24 million fee for a $100,000 ethereum transaction - but the miner agreed to return it

• Crypto exchange Bitfinex on Monday accidentally paid $24 million as a fee for a $100,000 ethereum transaction.
• Yet the miner who verified the transaction and received the fee has sent most of it back.
• Bitfinex's mistake was an example of a "fat finger" trade and may be the biggest ethereum fee in history.

A crypto exchange accidentally paid $24 million to send $100,000 over the ethereum network, in one of the biggest "fat finger" errors in the history of digital assets.

Yet Bitfinex was thanking its lucky stars on Tuesday after the miner who received the fee agreed to return it.

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Bitfinex moved $100,000 of $4, a cryptocurrency pegged to the dollar, over the ethereum network on Monday to the decentralized finance exchange DeversiFi. DeversiFi was spun out of Bitfinex in 2019.

Ethereum transaction fees have been high recently, as the network has seen heavy use. But even so, Bitfinex's $23.7 million fee (the cost of 7,677 ether) stood out as an obvious error on the $4 data page.

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DeversiFi - whose selling point is that it can help users avoid gas costs - acknowledged the mistake on Monday, when The Block $4 the transaction.

"A deposit transaction was made using a hardware wallet from the main DeversiFi user interface with an erroneously high gas fee," it $4.

On the ethereum network, transaction fees - also known as gas fees - $4 by an algorithm based on how busy the blockchain is. But users have to enter how much they want to pay, and they can bump up the fee to tip miners, to get them to verify a transaction more quickly.

"Fat-finger" trades are the result of human error in hitting a wrong key on a keyboard.

On Monday night, DeversiFi said the miner who oversaw the transaction was returning much of the fee.

Paolo Ardoino, chief technology officer at Bitfinex, $4: "Kudos to the miner for being proactive and fair" alongside a love heart emoji. He said the crypto exchange Binance had helped establish contact with the miner.

Read more: $4

Data from Etherscan, which tracks ethereum transactions, $4 that the miner had sent 7,385 ether back to Bitfinex, worth around $22.2 million at the time.

Bitfinex said in a statement: "In transactions such as these, the fees are shouldered by third-party integrations with Bitfinex." The exchange added: "We look forward to DeversiFi's investigation and to having this matter sorted on their side."

The $23.7 million that Bitfinex coughed up could well be the biggest ethereum transaction fee in history. And things could have gone much worse for the exchange, given that crypto transactions are irreversible and not subject to regulation.