I like my photonis tubes a lot.
Here on Arfcom there was a nice guy that sold a large batch of new old stock photonis tubes, both MX10160 format, and Mx11769 format tubes. They went for between $500-800 (seller grades them all based on gain and blems) and a lot of us here in the NV forum snapped them up.
Outside of this lot of used tubes, the photonis tubes in general are very expensive! The "supergen" has been phased out by the XR4, XR5, and Intens lines of image intensifier tubes, but buying a brand new XR4/5 from a dealer would be equal in most cases to buying new Excelis or L3 tubes, sometimes even more expensive.
I wouldn't hesitate to buy a photonis equipped NV device, and I would rate them around the same as the omni IV/V non-autogated devices, or even a little bit better. For a PVS14 type device, single battery housing, with the manuak gain control, I think around $1500 is a fair price, maybe slightly less for a fixed gain model.