I like the idea of telling them something like $750 to piece the top plus cost of fabric. They would also need to check with a long arm quilter to see what the charge would be to complete the quilt. Just a thought.
I have also heard it said they would have someone pick out the pattern they wanted and take them to the store to see what the fabric would cost and they usually don't want to spend the cost of the fabric and pattern much less a hefty sum for construction and quilting.