[shartacct]

They do, people trade in phones for credit towards an iphone all the time.

Doing it without the meagre compensation they give now would be deeply unethical, Tesla tried something like that recently when a story emerged that someone was quoted for full out of warranty battery replacement for a broken cooling hose fitting on their cars battery and they refused to give any core charge even though the battery itself was still fully functional (https://www.youtube.com/watch?v=n8-OkfCcRAo).