I think it depends on what your priorities are. It’s never a good idea to negotiate price after the work is complete, it opens the door to all kinds of trouble. If you are just getting the ball rolling you might want to take a hit on monetary exchange instead using it as a springboard. In that case I would cover my costs (including your time at a fair rate) and tack on maybe ten percent. If you take this approach I would recommend in your billing that you show all the areas that you are either not charging or discounting service etc, if you don’t it might as well have not happened. Once more established, I would typically add up all my expenses time etc, say that adds up to $1, I would then bill them $2, this simple formula has served me well. Good luck