Molly Crabapple's Rules for Creative Success.
If you haven't seen it, this article by Molly Crabapple about creative success is worth a read. She makes a lot of good points about not accepting anything less than what you are worth. I have done this to myself at times, offering "friend discounts" and lowering my rates. I realize now that this not only hurts myself, but the creative industry at large. Companies will almost always choose the lowest rate, so if you are not offering a comparable and fair rate for your work, you hurt everybody. The reason some companies don't value design is because there are people offering it at a rate that does not demand the respect deserved for the amount of work put in. So, you know....respect yo bad self. This is your job.