We bought a 500-foot spool of black Belden 8281 Precision coax a few years back to wire up a post-production facility, but it was never used. 8281 is considered the standard for professional video installations.
20-gauge solid copper center conductor
Solid polyethylene insulation (dielectric) and outer jacket
Double-layer braided shield, tinned copper, each with 98% coverage
We probably cut off less than 20 feet to test terminators, but the spool which got a little dinged up seems to have almost all of its original 500 feet (we are not going to unwind and measure). Check this pic of the actual spool.
500-foot spools of Belden 8281 sell for $400 and up today. We're asking only $180!
This is strictly cash and carry from my UWS location (a few blocks from 96/B'way, easy to reach by car from anywhere in the NYC area) no shipping or delivery. Keep in mind that the spool weighs almost 40 lbs.