fb ppc

Hey, what is the lowest you paid for a conversion? I mean how much you paid to make a certain amount? People keep saying average profit margin for ppc is around 35-40% of the total ad spend? Can you give some tips who are doing high in even numbers?

I have multiple .8-.10 CPC USA Target ads that work great on other networks but for whatever reason never convert on Facebook - does anyone have any advice for converting FB traffic? What would you say the standard conversion rate for FB traffic is?