Popunder.net seems to be long time in the business and I can see from their global stats that the top publishers are making over 30 $ per 1000 hosts. So that is the highest number I saw... I assume averages could be above 10 $ per 1000 hosts and all depends on traffic source and content. Payments are sent on request and minimum payment is just 2$. Payments are sent via Payoneer, webmoney, Paxum, epayments. Popunder says that in 6 years operation the traffic of websites using their code did not dropped more than 1% in traffic... or at least no one complained. So it might be good to try and see yourself.