Comment by Semaphor

I’d assume that with such a level of required inspection, you also have quite some security requirements. I’d say at that level nothing works as well as GrapheneOS (though you have to either delay security updates or accept temporarily closed source (they get access to the code only in exchange for not publishing it until X days or something) updates, thanks Google). As that currently requires a Google phone, the only way to get close to your price target would be buying it used.