If you are willing to sell it - but would much rather keep it - put a price tag of $10,000 on it.
Tell the potential buyer that it is "art" and that you are attached to it.
You could also tell them about the pattern and where they could get the stuff to make their very own - along with your estimate of actual cost of materials and times you spent on it. If they don't have the tools and machines you have, you could mention what they would cost, too.
I see paintings shown on Antiques Road Show that are valued at very high values - and I would bet most of them took a lot less time to paint than it does to make a quilt!
I think that if the item is/was NOT commissioned and the price agreed on ahead of time - one can ask what one wants - even if it seems unreasonable to a potential buyer.