The Surinam roaches: burrowing, pantropical, and built around the trait that defines their market, parthenogenesis in the widespread species, where every individual is female and every colony is self-founding.
They live in the substrate and surface to feed, which makes them the standard burrowing feeder for keepers whose animals hunt the ground: colonies establish from any starting number, tolerate neglect, and produce continuously.
Parthenogenesis caps the price permanently, and it carries the standard flip side: an escape is potentially a population, and in warm climates the species is already established as exactly that. Supply is universal, cost is structural, and the only purchase decision is whether a self-cloning soil roach suits the enclosure it would serve.