EnviroTO
Senior Member
The biggest factor in station cost below the surface is platform width, platform length, station depth, and vehicle capacity. After those three things are factored in there is no significant savings to be found elsewhere. Lowering the ceiling means supporting more dirt, the finishes are cheap compared to the overall cost, the accessibility and evacuation requirements must be built in. You can save money by having less significant pieces attached to that station box like getting rid of bus terminal buildings.