the 300/month is for the 5$ plan? possible "fair use"-like hidden limits aside, the 10$ sounds unlimited
from their front page they claim that "We do not log or associate searches with an account", and their privacy page is fairly detailed
Usually businesses changing privacy policies are the ones without a revenue model that need to figure it out somehow, and aim to IPO.
10$/month way more revenue than they could be able to get with ads, and sure, let's hope they don't want to IPO, because that's the root of all enshittification.