To a collector, an eMate with accessories can fetch at least $50. The biggest foible with these is the springs on the hinge slipping and piercing the video cable. Not too common, but can happen and is entirely fixable.
I had a lot of about 25 a few years back and sold them off ranging from cost of shipping to $50 - then I learned more about them and developed my own way of rebuilding the hinges from scratch (vice repairing the old ones) but i digress...
As for the inherent worth of an eMate, think of it as a laptop computer cut to the bare basics with no frills. I have two, one I use on occassion. It is basically like having an MP2100 with a built in keyboard (and a slightly slower processor).
The biggest strength is having Newt Works. It is the ultimate word processing app for any hand held.