Parcel by construction
The natural split is by family: medium voltage, tray, building wire, portable cord. Each parcel then has a coherent market and a single basis.
Keep reels intact
Never split a reel to balance parcels. Footage is the value, and a cut reel loses more than the split gains.
Count the overhead
Each parcel needs its own collection, loading and paperwork. Two parcels rarely cost twice as much to move, but five usually cost more than the price improvement.
Price the whole lot first
Get a single-lot offer before splitting. It is the benchmark, and sometimes it beats the sum of the parts once handling is counted.