For who interested the translation of the light novel: https://lightnovelstranslations.com/i-woke-up-piloting-the-strongest-starship-so-i-became-a-space-mercenary/
500k sounds like a lot, but if the enemy has no anti-torpedo point defenses then it's cheap for taking out a capital ship. To the point where I'd think cheap light torpedo bomber 'cavalry' would be a mainstay of fleet combat.
The crystal spiders emit an overwhelming shrieking sound that can be heard even in a vacuum. Obviously it isn't a natural sound, but it still sounds like one, so they automatically cover their ears.