I've been trying to think of a time when a situation like this had ever worked out for me, but I can't.
Maybe a simple way to look at is that it takes time to estimate and plan out a job that includes an accurate and complete material list. A markup on materials helps to pay for the time involved in laying out a job.
Quality and suitability of materials aside, sometimes things have to change depending on unexpected circumstances encountered. And having the flexibility to change methods and materials along the way instead of being committed to using what someone else bought can be a big deal.
Bill
