You are looking for a pleco to go with african cichlids ... (I'm not sure if you are looking for lake tanganyika, lake malawi, lake victoria, or riverine)
I'm not sure, but none of the plecos here get to a range of less than $2, even the most common is at around $4. They would get to around 12", some (depending on their personality) are aggressive and are nocturnal. I have one in a tank right now and another I gave away. The one that I gave away was always being attacked by a breeding pair of kribensis cichlids (Pelvicachromis pulcher) and I was starting to defend itself by trying to attack the male and the female, when they were attacking it for being there when their frys decided to go there. The one that I have right now doesn't want any other fishes around it's territory.
Usually plecos cost more than $2... If you go for cheap, they will usually grow too large for the aquarium.