Coinbase executive Conor Grogan posted that, according to his statistics, at least 913,111 ETH have been permanently lost due to user errors, equivalent to more than 0.76% of the ETH supply, worth approximately $3.43B. If we add the ETH burned by EIP-1559 (5.30M), then more than 5% of all ETH ever (23.42B USD) has been permanently destroyed.
Some of the largest historical Ethereum permanent lock-up events include:
The Web3 Foundation lost 306,000 ETH due to the Parity Multisig vulnerability;
Quadriga lost 60,000 ETH due to a smart contract failure;
Akutars lost 11,500 ETH in an NFT minting failure;
Users collectively sent 25,000 ETH to burn addresses for unknown reasons;
Conor Grogan added that the $3.43B figure is much lower than the actual amount of lost/inaccessible ETH, covering only cases where Ethereum is permanently locked, such as not covering all lost private keys or forgotten Genesis wallets, etc. The statistics come from various public reports and queries.