LOVE your quilt!
How do you want to value your time and materials? A king size quilt, even using scraps, will have 9 - 12 yards of material; you also have thread, batting, backing and binding. The more seams, the more material in the quilt! Easily more than $100 in materials.
How about your time? Did you put it together in one day? 8 hours for the $40 remaining from materials - sound fair??
Do you want to sell other quilts? Setting your price for this one sets you up for your next pieces - undervalue this and you'll have a hard time valuing your future work.
You can always suggest what the actual costs are, but that she is a wonderful friend and she is constantly helping you with this and that, you could part with it for the $140.
Sound harsh? I've come to believe that my time is my most valuable commodity.