Just as another thought experiment would be how much would it cost to get enough ETH while people are selling theirs to do this to launch your own 51% attack on ETH.
The fact that there is no real work involved just having enough money to buy enough of a specific coin has always been a weakness of all POS coins.
And now that there are ETH ETFs there is an incentive for people to be able to short the ETFs if they think their value will go down.
Think about it, get enough funds to buy the companies I discussed above that host a bunch of the ETH staking nodes, while simultaneously buying ETH and spinning up your own nodes and then a simple 51% attack against ETH.
-Dave
In theory, a 51% attack on Ethereum would cost > $300B × 50% = $150B. (Bitcoin and Ethereum have apparently just dropped 11% and 21%, respectively, in this past 24 hours.)
And a 34% attack would cost > $300B × 33.3% = $100B.
The stakers would lose that money (in a Rival Goldfinger attack), and they would only be able to gain $300B, and
only when assuming that the Bitcoin investors share the costs equally. If not, it would thus take at least 33.3% of the Bitcoin investors to participate in an attack in order to break even in terms of costs and gains. (And for a 51% attack, it would require at least 50%.)
Now,
if the Bitcoin investors is somehow able to keep their attack a secret, they would in theory not need to beat 33.3%, but only ~0.01% (in the current moment), which is the actual fraction of staked Ether compared to what's in circulation. But on top of the need to keep it a secret, this theory also assumes that safe guards like described in
https://ethereum.org/en/developers/docs/consensus-mechanisms/pos/#finality isn't implemented or doesn't work.
Last but not least, in order for the steal to be finalized for good, the attackers would also need to confuse the Ethereum community of whether the reorg was malicious or not, assuming that the remaining 66.6% of the Ethereum stakeholders would otherwise just revert the attack afterwards.
For a 51% attack, the attackers would be able to force a hard fork when the "honest" stakeholders revert the attack. But unless again the attackers can succeed in confusing the whole community, the community and investors will know which of the two chains they ought to support, if they don't want to support the chain that actively tries to undermine its own currency.