Lets just clear the air here.
Notwithstanding cash incentives from the Distributor, aka the "Company", new car dealers care not if the vehicle hits the curb financed, cash sale or lease, although financed vehicles do up the gross slightly. To the customer, price/monthly payment is the driver. To the dealer its volume. These two drivers bring the customer and dealer together. The dealer discounts to reach certain volumes. There is no special discount for "cash". Whether the reimbursement comes from the bank, captive, lessor, or the customer's wallet, its all the same to the dealer. That being one more unit on the board.
As far as ppl that pay with cash not originating from HELOCs; well they simply have money regardless how they acquired it; worked/saved it, got it from grandma, fell from the sky, it just usually means that they have more liquidity than the payment customer. PPl who claim that it's better to take low financing and then "invest" the principal are kidding themselves. I think it's more the case that ppl like to see $25K in their "savings account" and owe on the vehicle rather than not have that $25K "there" but own the vehicle outright. I refer you to Freud on that.
Why walk around for 5 years saving money to pay cash for a car? That's gonna add up to some serious shoe $$$. For those that qualify for captive financing, 5 year new car loans @ 2.9 and lower are the way to go providing you buy a Corolla.