Trading up a Studio Display - impossible

Studio Display trade in. A year ago I traded in my iMac 2017 5K for a new Apple Studio M4 Max and a Studio Display. It's really disappointing that Apple does not offer us a way to upgrade the Display. All I get is that I have sell it privately ... and that really says it all. So much for supporting long-term customers.

I don't care about the argument they have about parts, usage etc. I care to buy a product and want to upgrade a year later without the hassle of selling privately. I'm pretty sure I'm not alone. Given that I'd be still paying some £2k into Apple's coffers, it would be appreciated if they reciprocated the loyalty.