Good luck finding a continuous supply of people willing to volunteer so you can save money on paying people for their time.
BSAC for their recreational levels.
CMAS in some areas when also going through clubs.
Sometimes it's possible, sometimes it's not. Being cheap does not always equate to being bad.
The problem with cheap certifications is that for the majority of the businesses, there are costs that need to be covered and when something is really cheap, they can be cutting on fundamental things. And many divers may not know what to expect and therefore not know if things were done properly or not.