All my cost + contracts have a cost + 10 to 25% of materials PLUS labor at 45.00/manhour. This is clearly stated in the proposal and in the contract. All costs (including taxes)incurred for a job are billed. The markup is for the overhead you pay when you use your nonbillible time to get and account for the materials. Some one has to pay for all the "office" expenses. If you sell materials for what you paid for them then you need to bill your customer for your "office" expenses. I doubt that you will get a customer to pay for your business insurance when it comes due.