Not enough conversation in the world, in any space scientific or otherwise, talks enough about how efficiency is a measurement of scale in any given system.

A system can be efficient at large scale, and inefficient at small scale. This isn’t even only true of systems like “10,000 people ride inefficient train, so it saves 10,000 cars on the road, and the carbon cost of producing Teslas.” The SR-71 Blackbird can barely fly at speeds slow enough to take off. It CHEWS fuel on the runway. But at speed, it’s extremely efficient and one of the most capable objects we know of.

It might not do well if only 50 people ride it a day, but those old diesel train clunkers can move a lot of people.