Earlier quoted context omitted.
What's the future value of oil in a solar or nuclear powered world? It's important to know that when considering the factor of 5 million you toss out there.
Pretty high. It is a primary source of long-chain hydrocarbons, a primary feedstock for chemistry. Most biologically active chemicals produced by industry rely on oil as the chief starting material.
Natural gas as feedstock to the Haber-Bosch process and coking coal in steel production, for reducing ore, are both much more formidable. They account for a large fraction the consumption of both (15% in the case of coal), and substitutes are difficult.
The story of where Earth's crustal iron comes from, when, and how, particularly as banded iron formations, is another interesting story.