It is for this and many related reasons that we found the exact car we wanted, took the VIN to our bank, and walked into the dealership with a financing check. The dealer financing officer called our bank, gave them the price-out-the-door, and our bank gave them a PIN to write on the check alongside the total amount.
We walked away without having any further relationship with the dealership. Despite this, they tried several times to get our written consent to run their own financing. We steadfastly refused.
Not everyone is in a position to do this, but it was nice because we didn’t have to put up with any (other) dealer bullshit. (We did have to put up with other tangentially related dealer bullshit, which I have previously written about on here.)
Edit: typo and context