I don't need to send them any traffic.
I just signup to these BIG payments sponsors and then use my 6 credit cards to buy 6 trial memberships per day.
Why do you think lots of sites go out of business after their BIG pps signup brags on GFY? It's because they just cannot pay the handling costs of all these trucks loaded with money that they have to send to my office
And answering your question... it's never enough.