"certains" as a pronoun

i just read this sentence:

mais je n'ai jamais eu à accepter les tarifs de misère offerts par certains.

in english, u could use the pronoun "some" in some circumstances w/o having referred to people prior.  but i think it's more common in french.  in this case, it doesn't refer to a specific group, but it's understood to mean "by some people."