Building materials, payroll, truck(s) tools and other BS.
a good general contractor will make between 5-15% of the gross. So the more money you bring in the more goes in your pocket.
It cost alot of money to stay in biz. When it was just me, I didn't make a dime until about 5k in profit a month. when I had 7 guys, I had to bring in 45k a month before I saw a dime.
You can only charge so much, I was always on the high end of pricing, you got top end work for it, but you had to pay. Its why I never had to look for work and why People are still calling me now. I've had several home owners tell me they will pay for me to reactivate my lic+ all the BS just to come remodel thier " fill in the blank". If it was not for all the BS that goes along with being a contractor( not just state,but federal, the new lead BS comes to mind) I'd do it in a heart beat, but no way in hell now.