I don't get the buyer criticism of a ship being sold.
Buyer appears to think they will get a better price by pointing out deficiencies.
Even if they are valid deficiencies, the seller knows about them and it won't help your case.
It is insulting to criticize someone's airplane, so knock it off!
If it has deficiencies - individual or in sum - which the buyer cannot tolerate - then walk away.
If not, then take what you know of the market and how the current bird fits into the continuum of 'scrap' to 'mint' and make your respectful & unemotional offer - and await a response.
I don't know that I entirely agree with what you said on this one. I'd never intentionally try to insult someone, or their aircraft, especially if I was trying to buy it. But, pointing out material deficiencies is part of purchasing anything, especially if the seller is trying to downplay those deficiencies.
I have a diesel truck that I use for pulling our horse trailer. Back when I first bought it the seller was asking too much, having priced it on the higher side of an "excellent condition" vehicle (based on blue book values). I decided to put an offer on the truck, but wasn't about to pay the seller's asking price (or anywhere close to it) for this truck. I wrote up an offer, and explained in detail about which material deficiencies caused me to lower my price *significantly* below his asking price. I was very polite in my offer, but I didn't pull any punches on the vehicle's condition. I called the seller before submitting the offer, and told him I'd be sending him the document.
The seller called me after I submitted this offer, and told me that he'd think about it and talk to his wife, but he didn't know if we'd be able to reach any kind of agreement (if I recall correctly my offer was a solid 25% below asking price). I told the seller that I completely understood his position, but wanted him to at least know where I was coming from with my offer... then I waited. I was expecting a counter-offer, but the seller called me up about an hour later and agreed to sell for the price I submitted to him.
I NEVER insulted him, but I certainly pointed out every material defect I saw that wasn't originally disclosed in the advertisement for the truck. Why wouldn't I do that? Sure, the seller knows about them (presumably). But, the seller is trying to downplay those deficiencies if they haven't priced the vehicle accordingly. The same should be true for aircraft, at least in my opinion.
EDITED TO ADD:
Admittedly this tactic is far less effective when the seller has already disclosed all of the material deficiencies right up front. I had a couple buy my used lawnmower this spring, when I replaced it with a new one. I placed an add on Craigslist, and detailed the condition of the lawnmower very well (disclosing all deficiencies). I also posted a lot of pictures.
The female half of this couple called me, negotiated a price with me over the phone (wanting to pay $25 under my $150 asking price). I accepted her offer, and the couple came to buy the lawnmower.
The guy showed up and started trying to play hardball with me, murmuring about "Oh, there seems to be scratches on the deck here, and the handle is loose in this spot... what can you do on the price because of that?"
I just responded: "The price is firm. Your wife already negotiated your price, and I disclosed all of these issues to you before you ever drove out here".
The guy acted like he was going to walk, and I just told him to let me know when he made his decision. He paid the price we'd agreed upon.