Well, it's over.
I managed, (with the ideas suppled by members of this forum) to get them to raise the value of the damaged C 300 to at least low retail. Promises of a diminished value claim from my insurance claim and a call to V-Tail's supplied Mercedes Benz customer service honcho seemed to wake them up a bit. Stamped my little feet, threw and caught an F bomb or two.

Not sure how I did, but the head of sales and the GM didn't acknowledge me or the wife today. They both recognized me.
We left with a '20 Jeep Grand Cherokee Summit with 21k on the clock in exchange for 27.5k$ and a damaged 300C with 96k miles.

In my mind when both sides are convinced they got hosed, it was a fair deal. I got hosed but I hope at least they felt some pain.

OZ

That's a lot more than I got for my 15 C300 Sport, when I traded it in, in 2020 w/ 67k or so on it.