The reason why it's worth it is because these company sell these useless products for like $50-100/bottle. The distributors cost for these miracle cures is something like $3-5/bottle. So, they tell spammers that they'll give them $25-50 per referral. So, if these spammers send out 100,000 e-mail and like 1,000 (or 1%) responds, that dude has made $25,000-50,000 for just sitting at their computer and clicking.