Just say no...thanks for the compliment....Most people will not pay the cost it takes to make a quilt and expect for 1/2 nothing. Unless you really love quilting and are not interested in making money then take it on and have fun ..Or give them your honest figure and I bet they don't bit....But make sure they know the cost before you start buying fabrics...You might want to get a deposit if they are serious of 1/2 the cost of the fabric. This way if they back out you have something on the cost.