Generally recycling aluminium is incredibly cheap, especially if it's just a solid block without the regular potential contaminants, although I don't know what specific alloy they're using. If it's something like 6061 then it's especially easy to recycle, afaik, because it's very low in silicon and iron.

Do you know of any large tech companies that have more environmental ethics? I'm not sure Apple is good about it, but sadly I don't know of any better.