Not rare, and very generic... They're "hard to find" becuase they were thrown away.
So the Esprit is one of about a dozen model names that Kingman produced in the early 2000's. The (typically blue) esprit was the "how cheap can we make this thing" model. I bought mine for $98 from PBgear.com.
It's a slim striker gun, which is the "less reliable" version of the spyder. It requires really careful feeding if you want it to be reliable. That means, you need freshly charged (or ideally, external and big) batteries to make the trigger frame do it's job. You need a good air system, that's putting out 750-900psi, and does that consistently, and you need to make sure the gun, both valve side and striker side are well oiled.
This is not something most people could handle, (and most buyers were not "good owners") so very many of them met drill presses, or just trash bins.
For $26, you didn't do badly, but given the usual condition of a used spyder, Doc may be correct in you overpaying.
The board that comes installed on that gun, does 8 or 14bps, with no 1 shot queue, so if you're pulling the trigger rapidly, you'll get a "no shot" instead of a "slightly delayed" shot if you outrun the guns rate of fire.
I used a lightly modified Esprit for a year of tournament play. It was ~more reliable~ than the new shockers at the time, but it was less reliable than my cocker. It was however, really, really fast. (I had one of NotEvil's boards in it, fed it with a good air system, and a halo.)