The thing that matters is how valuable the 32ETH stake the validators put up is as that is the amount of penalty for trying any attack. The theoretical attacks on Proof of Stake are well known and discussed but generally require 33% - 51% of all staked ETH for various annoying attacks on the blockchain but not actually killing it.
3,491,906 ETH is currently staked right now which is actually way lower than will eventually be staked when PoS goes live later this year. 33% of this is 1,152,329 ETH which at current prices of $1,776 puts a minor attack at over $2billion. This is without considering that after the attack the network could easily fork and remove the attacker's ETH from existence so it's hard to see economics working in the attackers favor.
A high price of ETH means it costs an increasingly astronomical amount to attack the network and pretty much no way to do it profitably.
But acquiring ~1/3 voting power is much easier when 32 ETH are worth ~$3.2 vs when they're $60k
Also: People stake ETH under the expectation that the ETH they generate are worth just as much or more as the ETH they staked. If the price would continuously go down, less and less people would stake. The less people stake, the easier it is to buy 1/3 of voting power.
3,491,906 ETH is currently staked right now which is actually way lower than will eventually be staked when PoS goes live later this year. 33% of this is 1,152,329 ETH which at current prices of $1,776 puts a minor attack at over $2billion. This is without considering that after the attack the network could easily fork and remove the attacker's ETH from existence so it's hard to see economics working in the attackers favor.
A high price of ETH means it costs an increasingly astronomical amount to attack the network and pretty much no way to do it profitably.