.23 isn't bad, thats a good cost, .02 is more myth and not quality clicks. It really depends on what your selling and how many clicks it takes to get to a sale. Your question is too broad without understanding more about what you are selling. You have to remember you are probably not the only person with these emails and there is limited newsfeed space, and these people probably fall under other demographic targeting that people are using. Its an auction at the end of the day.