Read the rest of my post :)
Reasonable = Break even - which is all I ever hoped to receive, I only did it for fun and as a side project. When I implement the premium features I suspect to increase this given the amount of interest and my experience with other similar games.
Games like this are based solely around a community, people get friends on these games so don't wish to leave - the game itself is just an addon to the community.
Oh, and its more than $20, I think people must just be clicking as they want the game to survive or something - I've no idea. Not to mention I'm getting spammed with evony ads. I also suspect having a very direct advertising target helps, compared to other sites which often have a very broad market and thus struggle to advertise.
To be fair, I recently started a text based game (nothing but html, JS and a few minor icons - no flash) at the beginning of last month and I'm making reasonable money purely from ads - a single ad, in an unobtrusive place.
I haven't even introduced the premium features yet - people get very addicted to these games and are happy to pay for UI enhancements. Hell, I've ever had multiple people contribute designs, graphics and JS to the site wanting nothing in return.
It's been running less than a month in beta and has had 0 public advertising (this being the very first time) and has 150 active players purely from word-of-mouth. Admittedly its not making any worthwhile money currently despite me putting hours and hours of work into it but its been great fun and a great learning experience so its worth it never the less - so long as it breaks even I'm happy. - http://islandor.com