I found that the insulation in extension cords weighed 66% of the total weight. The cord I'm talking about consisted of an orange outer layer with a Green, Black, and White wire in the middle. I did a little math and discovered that I was making the same amount with or without the insulation, the only loss was my time spent stripping the wire.

Insulated No#2- $1.20 per lb (33% copper 66% insulation)
Bare Bright- $3.60 per lb (100% copper)

This is a very close estimate to what the yard was paying me at the time. If you think about it, every three lbs of insulated wire = 1 lb of bare bright being that 1/3 of the insulated wire was copper. You're getting payed for the insulation, so it is literally the same value at my local scrap yard.

If this was confusing for you, let me know and I'll explain it better.