https://www.vice.com/en_us/article/z3e4v8/someone-mysteriously-paid-25m-to-send-133-in-ethereum-cryptocurrency

Imagine sending $133 to a friend and being charged a $2.5 million fee. That seems to be the case for a cryptocurrency user who paid a $2.5 million transaction fee during a trade on Wednesday morning using Ethereum, a cryptocurrency similar to Bitcoin but with some key differences.

According to transaction details, which are publicly available, the mistake may have been in setting the price that the trader was willing to pay to have their transaction posted to the Ethereum blockchain, a permanent record of transactions. In Ethereum, like Bitcoin, users may attach a fee to their transactions to incentivize a miner to include their transaction in the next block of data. Normally, this fee is very low compared to the astronomical amounts that can be sent over the blockchain. Oftentimes, wallet calculators are used to inform traders what a good fee is so they don’t overpay.