My basic summary of the entire absurdity of the common tactic of "what's the best price you can do?" is as follows..
The best price is a vague concept depending on where we want to draw the line.
Best price I can do and keep my boss happy with my performance?
Best price I can do if I want to be below average at this company?
Best price I can do if I want to ask for a personal favor from my boss to allow me to heavily discount this car beyond established metrics we have and sell it this one time?
Best price I can do if I want to be yelled at tomorrow morning?
Best price I can do if I want both my boss and I to be yelled at tomorrow?
Best price I can do if I want my boss to negatively impact his career by the owner seeing him make deals like this too often?
Best price I can do if I want to get myself or my boss fired the next day? I could probably somehow secretly sell a car $10k under what I should... Once.
Where do we stop? Some nice people pay MSRP. Some people ask for a gesture of a discount. Some people ask for what discount is fair to market and we'd be ok with, and take it. Some people want below market, and we try to stop it if the car is in demand or we have enough volume. Some people want prices so low they'd fall into the "negatively impact the salesperson or teams career". Sometimes we even take those, but it's always a calculation between taking a below market average offer or waiting for one of the earlier described people to walk in.