I have found out, that on average after burning the insulation off, plastic coated wire weighs up as 1/3rd plastic coating & 2/3rds copper wire.

ie, from 100 Kg plastic coated wire, you would get 33Kg plastic coating & 66Kg copper wire

(in fact, I probably get 33Kgs toxic polluting plastic fumes, 60 Kg copper wire & 6Kg Copper oxides.. if I'm lucky)