Composition beats tonnage
A large lot made of one construction in one size is easy to place. The same tonnage spread across forty constructions takes weeks to market, and the offer reflects that.
Concentration risk
If a lot is mostly one cable that the buyer already holds, the marginal value falls. Conversely, a lot that fills a gap in demand prices well.
Freight economics
Large lots amortise transport better, which usually works in the seller's favour, provided the reels can be loaded efficiently and the site allows a full trailer.
Structure the sale
Splitting a large lot into two or three coherent parcels often produces a better total than one take-it-or-leave-it package, because more buyers can bid on each part.