Not true. Dealer makes money on the financing. If they are making money on that they can afford to sell you the car for less. Usually a good idea to walk into the dealership and let them believe you are going to finance the car and at the last minute change your mind.
I wasn't inferring that you could get a better price from a dealer by paying cash. I was referring to not financing the purchase of something that will depreciate.
Even if it's cash you have sitting in your checking account, there's an opportunity cost associated with using it. Lots of people have no choice but to use financing in any case. And, if there's some special 0 percent financing or whatever deal, it may make sense to use dealer financing rather than pay cash even if you have it available. You just have to look at the numbers for the specific transaction.