Hyundai Motor America does not own the dealers who sold you the car. The dealers are independent businesses (by state law).I would normally agree with you. But, when they are selling at MSRP which is waaaaay over cost to make it.....they are making money. There is no penalty for prepay. So you can make extra principal payments. You can also do that to any loans you take out without pre payment penalties.
Whether you pay the dealer MSRP or pay $1000 under invoice, it makes no difference to Hyundai Motor America or Hyundai Finance. The amount of money that Hyundai Motor America gets from the dealer doesn't change based on how much you paid or how much profit the dealer makes.