Recently a G/C who I have done work for questioned me about an invoice he received from another E.C. that was used by their firm. I looked it over and found that his price overall didn't seem out of line but his material cost was extremely high and his labor seemed unreasonably cheap. They had compared it to similiar work I had done in the past and were using my invoice as a kind of a benchmark. Is it common to "lowball" the labor and "pad" the material? I have always marked up my material a fair amount and charged my labor at a set hourly rate.To someone not familiar with mat costs, it makes me look like I'm raping them on labor. Any thoughts.