Bids come down to materials, labor and the size of the job... we all bid the same way. Some contractors cut corners on materials and labor explaining why their bids are low.. others cut overhead costs by not being properly licensed and insured. The old adage that you get what you pay for is actually true. Choosing a low-bid or negotiating a lower rate may make the job cheaper, but it forces the contractor to cut corners to get under budget... costing you more in the long run.