Agreed - you should always look at all-in costs, including financing. Normally better to get financing somewhere else ahead of time if you have good credit.

That is still misleading from the overall profit picture because the dealer can be getting points back on the loan.

That doesn't effect the price you ultimately pay, just who gets what.

(E.g. your "true" interest rate is 2.5%, the dealer gets you to take a loan at 3.9%...they pocket the 1.4%)