Well if they were unfixable, the company surely wouldn't have been able to re-sell them, would it? A refurbishing company whose phones die within a few months

Well if they were unfixable, the company surely wouldn't have been able to re-sell them, would it? A refurbishing company whose phones die within a few months wouldn't survive for long, and that's generally not how hardware defects work anyways. Things you can "patch up" only temporarily are very uncommon, so these devices would probably get an extra year of life at the very least, offsetting any possible shipping "cost". And even those that can't be repaired in the Archimede's ship sense, would go to shops like Rossman Repair Group that would use them for parts in fixing other damaged devices. Even if they only use one dead phone to fix one damaged one, that is still a net positive than if the damaged one would've had to be fully replaced.