what i do with materials, i just charge an extra 20%, and that usually covers my fuel and time spent getting the materials. if the materials cost $500, i get $100. but if the cost of the materials at 20% is less than $30, I charge $30. It usually covers fuel and time and the estimate (which is "free" but the charge gets worked in there if i get the job)
My set up:
-2007 Chevy 2500hd 8.1l 4x4
-7x18 enclosed trailer
-Grasshopper front mount 61", gravely 52"
-36" Gravely Walkbehind, 21" exmark push mower