LocalMatt Apr 23, 2019 05:01 PM Dog Park on State & De La Vina Factotum. Projects do not necessarily cost more than estimated. The engineers estimated cost present to give contractors a baseline for bidding. 9 times out of 10 the contractor who has the lowest bid is actually lower than what was actually estimated by the engineers. Also when a construction company is the lowest bid it doesn't mean they automatically make money for that job. Contractors take on all the responsibilities and costs. So if it takes longer and they screw up during the job the contractor could go in the negative and lose money for that job.