Nobody said that the ACV is what the dealer paid for it. I'm surprised anonymouscarguy reacted to your post as if he just learned something new. Maybe he's confused.

his "clearout" price is less than what he paid for it. He showed me the purchase agreement document from the MB dealership, and a form that declares the "ACV" or "actual cash value." Sure enough, the ACV is actually two thousand higher than his "clearout" price.

There's three numbers there, in order of appearance:

1. The "clearout" price (what the OP would be paying)
2. The dealership purchase agreement price (what the used car salesman paid the Mercedes dealer for this trade-in)
3. The ACV price (which plays little role and the OP should ignore if he wants to negotiate properly)

The dealer clearly admitted he paid less than the ACV (#2) and that he intended to make a profit (#3). Now, the question is whether he actually paid what the purchase agreement document from the MB dealership says. If he can offer price #1, my guess is no.