Buy a copy of Consumer Reports magazine and look at the ad on their back cover about car buying. I used their printout (which the no longer offer, but do offer a buy service that is equal) in the past and saved bundles.
I had a dealership offer a lower price than the Costco price because it was the end of the month but they didn’t have the color I wanted. I found what I wanted at another dealership and they matched the first dealership’s low price. Shopping around works.