I am a builder working on a higher end, new construction home. I am looking for ways to handle mark ups on change work orders for materials being purchased by the homeowner? We normally add on 20% for materials on change work orders (The contract just states that all change work orders must be approved of in writing). We are crediting homeowners for certain items on contract and they are purchasing their own much more expensive tile, subzero appliances, lighting fixtures, kitchen cabinets (they are not giving us their cost). They are having a hard time understanding that we do have to add on some kind of mark up on materials even if they purchase them, we will be responsible for these more expensive materials. Has anyone here had a similar experience?