The Mars aspect of SpaceX future impact will be less important than how 25X the speed of sound travel transforms our world and has huge economic impacts.

Geoffrey West and the Sante Fe Institute performed a study of cities and found that if the size of a city doubles, then, on average, wages, wealth, the number of patents, and the number of educational and research institutions all increase by approximately the same degree, about 15 percent. They refer to this systematic phenomenon as "superlinear scaling": produces, and consumes, whether it's goods, resources, or ideas. Reusable rockets could create a global city of 9-10 billion people by 2050. This would be a "city" with ten-doublings over a ten million person city. This would be a 150% boost in per-person income.