If you did not agree to the second offer, by now the sales manager has probably come to the desk to help his salesman close the deal. Subtly this presents additional authority to the situation, and does not work in your favor. The manager may claim expertise based on how long they have been in the industry, how knowledgeable they are about car prices, and may start to ask you why you feel you deserve “too low” of a price.
Again, the best way to deal with this is to already know the full price of the vehicle, the manufacturer’s rebates, and the dealership discounts before you wander into a dealership.
Otherwise, how do you really know the actual price?