Used to scrap looking back into it.

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Time is money! If I have a limited amount of scrap and am not picking volume at that time, I find it worth while to separate certain types of steels and alloys (rotors, flywheels, heavy steel, then alum rims, motors and pumps). I've found that personally disassembling large components like engines for heavy vs shred is not a worthwhile time/return investment, but if you have some time on your hands, it does provide more.

Copper is usually always worth separating and cleaning IMO. If there are any components you have questions about being worth your time to separate or not, google is a wonderful tool