I'm told that copper wire used for electrical work is first use copper only, meaning that once it's processed from ore it's pure enough to be used for electrical. Recycled copper is used for different things like bronze and aluminum alloys, it doesn't pass current as well as first us and builds too much resistance.
One of my service calls is a wire pulling place where they take what looks like 3/4' diameter solid copper wire on a big spool that comes straight from the mines and pull it into fine strands then twists them together into different gauge wire and finally vinyl coat them in the different colors . These are then wound onto large spools and shipped out. I would imagine they sell these to a third party who winds the smaller spools you would see in a auto parts or home improvement stores.
The copper in the wire is a commodity with it's price changing with supply and demand. Currently, demand is low and the mine has slowed digging ore.
With that said, I don't think matters as long as you stay with the correct wire and covering for what you are using it for. An example is for automotive, use stranded wire with a oil and solvent resistant covering. Don't use a solid wire with a cloth covering.
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