I've always told the person that the cost would be over $200. Nobody has expressed an interest beyond that.
People have no clue just what the cost of materials are for a quilt. They think in terms of the quilts at Sears that cost $50. Even my Mom can't seem to get in her head how much fabric costs. She still thinks in terms of $1.50 a yard (she hasn't sewn in 30 years). At $100, you are barely covering materials, assuming everything is clearanced priced!