They're usually quite nice, though it varies quite a bit. Government contracts typically have very long equipment lifecycles, so some models you find may actually be using quite old LCD technologies with corresponding contrast, brightness, etc. limitations.
The last time I looked into these, they tended to start at around $3-5,000 per unit and went upwards of $15,000 in some cases. Probably outside most peoples' budget. Pocket change to Uncle Sam, of course.