Architects generally recommend bidding because they are not sure what the cost should be. They have been taught to believe bidding will assure them of the lowest possible price . The fact is bidding only assures you of the lowest possible bid - a significant difference. The final project cost will always be more than the bid price.
Bidding is a game that is played in two parts.
In part one of the game, each contractor's goal is to try to out-guess the others in determining the amount of the profit to include in their bid. The one who guesses the lowest number, without placing their company in financial jeopardy, wins. Because part two of the game begins. Since the winning bidder has reduced his profit margin in order to win - he must now become your adversary. He must figure out how and when he can cause a desire in you to change as many areas of the design as he can.