When the offer is $X now or $X/36 for 36 months, it's clear the seller is paying the financier, but that doesn't mean the seller will offer a discount for current payment.

Some do although, especially when you poke them about it. You see it often with cars where you offer all cash vs the %0 financing option, you can often get a discount that way. The $2000 in interest you were going to pay implicitly through the inflated price of the car goes away.

Sure, but as there were no full payment discounts, full cash buyers subsidized my payment plan.