He is really stupid or a crook.
A new controller will have to be programmed. It doesn't actually get anything added. It is only variant coded. The programs are in the unit and are located by installing the variant code number either from the parts info or the old controller if it has any smarts left at all.
What is so stupid is trying to sell a car that valuable, not running, due to a $200 cost. If I were advising on this purchase, I would subtract 10-20k from the price. Without running you can't check engine, trans, or A/C. Yea, I'd give him $20,000 off book price in that state, what a fool.
Bosch Master, ASE Master, L1
33 years MB technician