There is a real authority in having prices, costs and details in print. Printed material carries an inherent believability. If you are a buyer, you may choose to have target prices, or competitive prices, or last year's prices. You may have a printed page detailing the implications of proposed prices and their impact on profit, on staffing levels, etc. You may even have a summary business plan built on your ability to achieve a given price for this contract. It is so simple but so effective it intimidates the seller into a defensive posture.