The waterjet is especially flexible compared to a milling machine. The small kerf means you can create smaller features. There's no need to change tools dependi

The waterjet is especially flexible compared to a milling machine. The small kerf means you can create smaller features. There's no need to change tools depending on the material type. Chips are automatically blasted into the catch tank, instead of accumulating on the workpiece. Waterjets also typically have a much larger workbed compared to a milling machine, so you can load an entire 4x8 foot sheet and cut a bunch of different parts, or one big part. I think you're right, though. For occasional prototype parts you're probably better off either ordering waterjet cut parts from an online service, or running them in a small CNC milling machine.