I encourage everyone to spread this video around. I completely agree with what he is saying and people who are serious about art should also follow his advice:
http://youtu.be/oWXYoD7wfOs
Don't let anybody ever swindle you. Even if you're not a level you think is professional, don't devalue your artwork. This is also aimed at people who undercharge for their commissions. Your time, your art, is valuable.
Original linked to me from ~reiq (https://www.deviantart.com/reiq)'s journal.