I have seen dealers trying out that approach before, and the offer, in terms of the percentage of the listed price, sounds about right. Basically they are watching market reaction/sentiment and/or hype surrounding a particular car and then try to knock the seller down in order to get the car as cheaply as possible.
Does this dealer deal in classic cars or high-end motors, or both? This would be a good information to have..........
I recently had a very similar experience with my 993RS, by a so called specialist who tried to knock its price down, but they made an offer, viewed the car, agreed that it was as per expectations and then knocked back offer back further..........and the reason, because it had non-standard wheels fitted (FYI: The wheels were lighter and used in race cars!) - they did know about the wheels before they viewed the car. I then found out that they have a lemon of a 964RS in their stock (that car did not have original wheels, RS engine or gearbox)! The price has just been reduced by £15K, so somebody may have pointed that out to them. Now this is a "high end dealer" based in a posh part of London. So seems like the Vee is getting on their radar too...........