Custom forge tooling for head tube vs turned bit of ally tube.
Custom forge tooling for BB yoke vs no BB yoke.
Custom forge tooling for dropouts vs off the shelf dropouts.
Custom tooling to bend the chain and seat stays vs Unsure, but unlikely to go to anything like the level of detail Inspired do.
Butted tubing vs plain tubing.
Multiple process finishing method (the red frame is actually prepped and sprayed in gold, then has red lacquer added, then the graphics, then clear lacquer) vs basic black paint.
The Inspired frame probably costs double (or more) to produce when you factor in a 'cost per item' on the tooling...
Oh, and what JD said.