OP… “Maybe the manufacturers agree to take it back in some crazy financial maneuver to get it off the market.”
Ok, now that is a crazy conspiracy theory. My dealer takes trade-ins and sells them to a company that assesses and then either sells them on-line or to a reseller. There is not a high end company that could afford to do what you suggest. Some offer their own trade-in policies to do what you say, but they have very tight controls on it and limited payback.