Tough to say what it is. There are a number of fish that go by that name, including some that aren't even in the loricariidae family, but rather a loach. Can you give a better description?
Butterfly pleco is the main common name for Dekeyseria brachyura, but other Dekeyseria sp. have adopted it, and as Wyldfya stated, common names can be given to anything, and I've seen plenty of plecs given the "butterfly" name.
The ones I saw looked like "royal" plecos, in that they had longer finnage compared to the common pleco. It also seemed like their black spots were darker and the brown was more vibrant
With Petco...they don't have anything unusual. The Petco by my house sells "Butterfly" Plecos and they are really Sailfin Plecos (Glyptoperichthys Gibbicep).
i bought a "butterfly pleco" from a real good fish store, not a chain store like petco. it turned out to be a hillstream loach. i bought mine for $6.99 so maybe $10 is overpriced?
maybe.
unless you keep them in cool water they are always overpriced. They don't do well in tropical temperatures and unfortunately they are often sold as tropical fish.
the ones at petco are gibbiceps look at the latin name on the tag that is the only "butterfly pleco" we sell the hilstream loach is sold as a "butterfly loach"