Cost of a roof varies depending on the size and if there is more than one layer of shingles already on. Also for any holes in the wood structure they will need to replace wood boards. I just had mine done two weeks ago and it cost me $7,200.00. I had one layer, needed wood planks and put vents in.
The roofing price changes depending on the choice of roofing materials used, roof size, steepness of roof slope, and general complexity of the roof. The price of labor would be added in that to.