A rocket eats its fuel. The tenth flight costs what the ninth did.
A factory that builds itself does not. That is the entire difference between shopping and gardening, and it is the only thing standing between us and a Kardashev-1 civilization.
The number that decides it has no name, so here is one: the closure rate — how fast a self-replicating factory climbs toward building all of itself from local material.
At 90% closure, the Moon multiplies Earth's launch capacity by 10. At 99.998%, by 50,000.
Same rockets. Same Moon. One number.
And it is worse than a slow start. Below the threshold you do not get a slower exponential, you get a straight line. A lunar industry that works, and never compounds.
On a 40-year climb: 100× cheaper launch buys ten years. Six months off the replication cycle buys thirteen.
We have spent billions dollars driving down $/kg to orbit. It is the right problem to solve. Soon it is no longer the binding one. @elonmusk understands this and $SPCX has started building the seed.
Every serious plan now specifies the rocket and the seed. None specifies the closure rate yet.
It is the most consequential unmeasured number in the world.