In normal power distribution, much of the cost is in generating the electricity, and the cable is cheap and readily accessible and you can easily take several t

In normal power distribution, much of the cost is in generating the electricity, and the cable is cheap and readily accessible and you can easily take several truckloads of heavy cable to the many sites. Undersea cable is different, and I suspect that nobody cares if 99.9% of the power is wasted to heat the power wire as long as enough gets to the repeaters. Kirchhoff's law says that if your wire is insulated, ask the current that goes in one end comes out the other. The only thing is that you need to provide sufficient voltage to push it through the long wire.