I think that most people think they are going to get a bargain if they have someone make something rather than by ready-made at a store. And, I also think most people do not have a clue what fabric/notions cost!!! I imagine in this case you have a good reason for not pressing for pmt for you time but I sure would (in the future) explain that in addition to the cost of the materials that you will need to be paid X amt for your time.