ratio question for free signups

is a 1:3 ratio on a site like webcams affiliate program ($25/free signup) suspect at all? im not really doing anything other giving incentive for users to signup for me..

wasn't sure what kinda ratio to shoot for on affiliates that offer pay per free signups.

I thought it was up to 50%, but after some of my reading in BHW it appears a lot of the affiliates don't pay anyway. I just setup porn based affiliate links today on a shitty site i have.
I don't actually expect they will even pay but more for my own learning and hopefully one day earning.
My $2 of from google isn't quite cutting it. (that's in a week also)