This is really only applicable to buying new things on ebay. Last gen electronics are the only thing I buy new on ebay but even then good deals are pretty rare. At this point if you want a good deal you need to go back 2 generations usually. I saved around $800 on my macbook pro by buying a 2021 model NIB on ebay a few months ago. Asahi linux only runs on m1 anyway so that was my prefered processor over m2/3 anyway.

At least with apple, the warranty only starts when the product is activated, so as long as the original plastic wrap is still on it you will get the full factory warranty.