I calculate that the 57,000-tonne Skyhook hub would require about 500 launches of Saturn V rockets each with 125-tonne payloads, and would take about 38 years to complete.

Alternatively,

The Skyhook hub would require about 250 launches of Energya rockets each with 250-tonne payloads, and would take about 20 years to complete.

Alternatively,

We could forgo the 57,000-tonne mass for the orbiting Hub, and instead rely on a multiply-redundant electrodynamic stationkeeping powerplant. Power would be beamed in a highly reliable manner from earth's surface to the Hub and transformed into propulsive energy. A failure of this system would destroy the skyhook completely, but might allow faster construction.