It's difficult to have a win-win situation when one of the three sides is getting paid a massive cut continuously without contributing anything. Next time give your friend a one-off finder's fee upfront and deal exclusively with the client from there.

> And I am willing to go as low as $15

So if they offered you $14 an hour, you would drop the project? Despite working for $9 so far and having another client at $10? You'd better be able to walk away from this or your leverage is non-existent.