Blue-eyed plecs,
Panaque cochliodon, are not rare in the wild. The problem is that their natural habitat is Colombia, specifically the parts "run" by the drug barons. It simply isn't safe for fish collectors to go to these rivers anymore, and thus you don't see wild-caught fish on sale. As others have mentioned, they used to be fairly common in the trade. I had one during the late 80s and early 90s, and it cost around £10, which, allowing for inflation, would be comparable to an inexpensive oddball plec today.
One of the downsides to this particular species is that the wild-caught fish were often very sickly. While this is sometimes true for other
Panaque spp. as well, compared with royal plecs,
Panaque nigrolienatus, blue-eyed plecs seem to be much less easily restored back to health. The pathogen has been documented in the scientific literature, and is a bacterium similar to
Rickettsia spp. (which in humans cause things like typhus).
http/en.wikipedia.org/wiki/Panaque
http/en.wikipedia.org/wiki/Rickettsia
They are attractive fish, though very shy and somewhat picky about water conditions. Many old aquarium books refer to this species as
Panaque suttoni, a completely different fish.
Cheers, Neale