I think the best focus to take in this case is to assume the person is planning to pay you for the service they are requesting, so the first part of the conversation should be an agreement on the charges. I usually start with telling them the ball-park figure is $400 and I have found that usually puts a stop to it. One young man wanted me to make him a quilt, and when I told him the cost, he started telling me about the jeans he had been saving and that I could use them for his quilt. I immediately explained to him the extra cost of cutting all those jeans into squares. He finally gave up.