For a typical board size of 18″ x 24″ (3 square feet) a board shop would add about $200 for low volume applications and about $90 to $100 for high volume applications to the price of the board. This adds between $0.21 to $0.46 per square inch to the finished board depending on the board volume and the technical difficulty associated with the board manufacture.
The added cost would be offset by the elimination of the discrete resistor costs and the costs of assembly, rework and inventory as well as the design and electrical enhancements to the finished circuit board.