I've made necktie purses and the ties held up very well. You would have to be careful to check the fiber content of the ties. If they are silk, I don't think I would wash them--dry clean maybe. If the person wants the necktie shape preserved, you could still open them (and they usually have some sort of lining/stabilizer already) retain the shape and just add the seam allowance, then sew together as usual.