It's the amount of money that makes it worth it. If they are successfull the amount is usually something like $10,000-$30,000. If they are only successful once every 2000 calls thats still worth it. Now you would say 2000 calls with 50 people in a call center means they are only successful once every few days and you are totally correct. But you have to put this into consideration with what they are usually paid. If you work in IT for huge companies like Accenture or McKinsey you will earn around 8-10k if you are in upper management and 6-8k if you are a normal worker. That's yearly. So every successful scam for these scam companies pays up to 5 peoples yearly salary