It is similar to a Pterygoplichthyspardalis but a Pterygoplichthyspardalis has a circle like pattern on it's belly where as a Pterygoplichthysdisjunctivus has wavy lines.
Exactly and what do you think a Pterygoplichthysdisjunctivus is? ... it's a common.
There are 3 plecos sold as commons:
Hypostomusplecostomus The original common... which is not so 'common' anymore.
Pterygoplichthysdisjunctivus and Pterygoplichthyspardalis have replaced the market for common plecos and grow much larger.
A Sailfin is considered to be the cheapest of the fancy plecos. Which can be bought at nearly any store as easy as a common. The price is higher(about double) of a common.