[taildragger]

The centrifugal compressor and the turbine are probably precision casted items, one piece, how they are attached and what materials is a different matter and maybe above our pay-grades :-)....

[expatpat]

The compressor, possibly, but you can't really cast the turbine section. High temperature materials require ultra-high-temperature casting.

The reason the guru says they are OK for just trains, planes, and buses is the high cost.