I have bought and sold various of them, and I could never find a "good" one or "keeper" for $25 either. The better ones worth using seem to always sell closer to or slightly above $50, with prices closer to the $100 for the really nice, mint ones still in their original, fitted, wood boxes. New ones can still be found on Ebay, but I have yet to see one sell for less than $100 (again, for a new unit). Here we are talking about their standard length units (6" range) - longer ones are even more. Pricing here is for the more common/plain inch models (no letters after the 123). Metric models (M after the 123) do come up from time to time, but not as often.
The most rare of all, the "combined" inch/metric ones (EM after the 123) - those seem to always command the higher prices on Ebay. The only "gotcha" with those is that you can only do OD with those, since the top scale (normally used for ID) is measuring OD in Metric (you can still measure ID but you have to add the thickness of the nibs in your head instead of it being a direct measurement). The 12" 123EM model that I trimmed in the photo above is one of those rare English/Metric models, and the one I use most of the time. The 12" model is heavier, sturdy, with even larger/thicker bearing surfaces, and it is my favorite of them all. Although still heaver than regular dial/digital calipers, my 6" 123 master caliper still feels wimpy next to my "trimmed" 12" model :devil:
Quick intro to the No 123:
http://www.starrett.com/download/62_123_caliper.pdf
More details, with all of the available models:
http://www.starrett.com/download/246_p108_114.pdf