Critical time

Including shielding Island one was to weigh between 9 and 10 million
tonnes - that would represent $100 million launch costs at $10/KG. According to my sources it was the Stanford Torus which weighed 10 millions tons. If we understand "Island One" to mean the Bernal Sphere design, that was less than 4 million, largely owing to its shape which was more efficient of shielding mass. But your other points are applicable to both, and well worth making.