StephenC ,
The StellarNet line includes spectrometers with deep (vacuum) UV capability, all using fibre optic probes. Almost certainly the fibre optics material gets more expensive with broader wavelength range capabilities, and the grating/diffraction system inside becomes more complex as greater resolution and broader bands of light are required to be processed.
The Bluewave is the next model up from the GreenWave, and goes to 200 nm standard.