Digikey PCB-Builder

The service is nice but only includes expensive board manufacturers. A simple two-layer PCB 2.9x2.6in on standard FR4 material rings $26.58 apiece when ordering 20 of them (adds up to $531), and falls to $4.06 when ordering 280 boards ($1k+). That's an order of magnitude more expensive than you can find elsewhere.

BTW what is those expensive board houses' specialty? Very large runs? Dozens of layers? Controlled impedance? Exotic materials for substrate? Space-grade reliability?