The dealer is presumably not influenced in terms of negotiated transaction price by whether the consumer goes with a manufacturer cash discount or the manufacturer 0% offer. If I am right, then your point is a wash because it remains the case that the foregone manufacturer cash incentive is an implicit interest charge. You get no more or no less negotiating room depending on what manufacturer incentive you choose, or so I assume.
Nope. You said that the choice is either 0% OR a lower price. It isn't. You make your best deal on price - then choose either 0% OR factory cash. So you CAN get 0% AND a "lower price". Or a negotiated discount plus factory cash.
It's true that you have no more or less negotiating room regardless of which factory offer you choose - but there is no "implicit interest charge". If you take the 0% deal, you divide your total out the door price by the number of months financed and that is your payment. Period. No interest. Cost of borrowing = zero.
If you choose the additional cash back, you take that additional amount off the price, figure out your payments with interest over the chosen term as per normal.
There's nothing hidden, implicit, misleading or deceptive - it's a choice - and a pretty damned good one. You choose to finance a larger amount over a longer term, 0% is a huge savings. If you are financing less over a shorter term, $4k off is a major league discount. One or the other will prove better for a given buyer, but they are both good. REALLY good.
I don't see where the confusion or controversy is coming from. Manufacturers do this to help dealers clear old stock so dealers will load up with more new stock. Simple as that. If you're in the market for a car that this appllies to (as my friend and sister were with their 2011 Genesis Coupe and Santa Fe, respectively - you are sitting pretty.
Jaeger