I have found that folks price such things based on what they themselves are willing to pay for it.
On the same topic regarding pricing but not quilt related I for years worked in direct sales and I was always amazed at gals that sold the product with additional discounts when the company already gave great discounts to begin with so there was no need for us as sales reps to give yet another discount. They were seriously cutting into their own profit.
Its no different with quilts. Folks will charge only what they themselves are willing to pay for that same item if they purchased it while others who understand making a profit will charge as high as 8-10 times more the cost of fabrics, threads, labor they had in creating it. These folks pay themselves what they feel they are worth and having made this item.
Personally I only make such to donate to charities, needed, and family members. If I were to be commissioned to create any project it would be based on what I feel I am worth for having created such a project which would include cost of all materials, ie, fabric, thread, time making it, designing it and such and than add a certain percentage over that total to make a profit for all my hard work and dedication to the project.