I do this stuff because the money feeds my habit -
I enjoy working on a project as much as the person appreciates me doing it. I may start out the conversation with "My quilt group gets $300(or whatever) or more to do this" and pay attention to their face. Then negotiate from there. I know that i never "make" any money, but consider the pay a token of my kindness.
I did finish a quilt for a woman - gave her a choice - a variety of things that I could do w/ a range of prices and then let her chose. It took some of the "hardness" out of creating a price, too. It came down to what I'd really like to get paid and how I'd do it, down to still meeting her needs and a cost that I thought she could probably afford.