Read this thread instead of playing Dota.
I dont know about trying to justify the charges... Limitless posted something about it not ending up being 5$ an hour, and dark0821 goes with the whole hourly thing...
If you have no fucking experience and the guy wants to give you money to do it, shouldnt a more fair price be a quote at a real shop - a certain percentage that you think is fair? If you charge hourly it makes no fucking sense because you spend more time on it, if anything it should be straight up flat rate @ 12 bucks an hour or something.