Even if next-generation vehicles like Starship reduce surface delivery costs by 10x, the mass problem remains. Shielding a single reactor still requires 8,600 - 20,580 kg of material. At even $100K per kilogram - far below today's costs - that's still $860M - $2B per reactor in launch costs alone. And a functioning lunar economy requires multiple reactors. In-situ manufacturing doesn't just reduce cost - it eliminates the mass constraint entirely. The raw material is already there, covering the entire lunar surface to a depth of several meters. The question isn't whether launch costs will fall. It's whether launching construction materials from Earth will ever make sense when the building material is already on-site.