I recently overheard a contractor bragging about how he could gain a cost advantage over his competition. It caught my attention, so I listened.
It seems that in his bidding practices, the contractor priced materials and equipment that were not approved in the specifications. To avoid giving away the bidding advantage to his competitors, the contractor decided not to request these items to be approved in the bidding period. After he was designated the low bidder, the contractor planned to press for the materials to be substituted for the specified items.