As with most things, it really depends. Generally though, you should expect fees on top of the actual ad spend since that usually covers the usual overhead (setup, management, creatives, etc.)
Not a hard rule by any means, but cheaper leads usually mean they're running grey or selling bulk, typically low-quality leads sourced via blackhat. Again, just an observation on my part. That may be of value to some, but it's risk-reward. Cheap doesn't mean profitable.