Renewable Energy World has an authoritative, detailed explanation of the economies of scale from building taller, more powerful wind turbines.
Example of 100-MW onshore wind farm:
25 towers @ 4 MW
25 towers @ $500k/tower = $12.5 million in structure + foundation
10 miles roads @ $1.5 million/mile = $15 million
Total infrastructure cost = $27.5 million or $275,000/MW
100 towers @ 1 MW
100 towers @ $350k/tower = $35 million in structure + foundation
50 miles of roads @ $1.5 million/mile = $75 million of road
Total infrastructure cost = $110 million = $1,100,000/MW
By increasing the tower size and turbine capacity, we can reduce the infrastructure cost tremendously.