Who is ends up paying for this in the end? I am not familiar with what this smart contract is doing. Were these user held coins or was it part of an institution?
Let's they actually had $320M USD ready and waiting. I assume the order book would not allow them to reach the fixed amount of ETH lost.
.. Sort of curious what would be the actual USD cost if someone actually tried to purchase the amount of ETH lost given a fixed order book. Do any exchanges make that information available where you could calculate that?
If you had $320mm USD and needed ETH, you'd want to use an OTC desk, because the markets will feel it, even though they won't actually run out of depth. Right now the "+2% depth" (https://coinmarketcap.com/currencies/ethereum/markets/) on Coinbase, Binance, and FTX is about 5mm, and there's probably a dozen other markets with similar depth, though you'd want to execute the trades simultaneously. Decentralized exchanges have depth too; uniswap's USDC/ETH pool would let you buy $40mm for 2% slippage. All in all, you could probably get it all at about a 5% premium if you were really prepared for it.