There can be no price put on a quilt made with love, made with expensive fabrics or from scraps. We just want our quilts 'honored' in some way and maybe as someone suggested somewhere or sometime your son's family will make their own memories of the quilt.
Maybe you know your DIL well enough and she might be like a SIL I had, she only valued a gift if she knew how much it cost not how much thought and caring went into it. If that's the case nothing you can do will impress upon her what your labor of love is worth.