Sleeper 321 Speedy on eBay

Sorry but I don’t agree that those situations are analogous for a number of reasons:
1) The roles are reversed in your scenario: the “old biddy” is the buyer that is “hard done by” whereas it’s the seller wrt to the watch;
2) there is far more and easily accessible information available to a person selling a watch. It is a one button process to see previously sold examples on eBay and determine what they sold for. Furthermore, there are resources like this site - people come here daily with this very question;
3) We have enshrined the idea of “buyer beware” into the law of the western world for a reason. We give people freedom to trade and, like a boxer, you need to “protect yourself at all times” or risk losing. The old biddy should do what is typical in construction: get multiple quotes. Problem solved for her.
4) The seller in the EBay purchase freely chose to list it for a BIN price. No gun to their head. Perhaps they didn’t understand the value, but if someone offered them via a PM $5,000, that should’ve perhaps clued them in that it was an item of value perhaps worth additional research;
5) The seller didn’t HAVE to sell the watch. When a roof is failing, you need to repair it or risk significant other damage;
6) Or, perhaps the seller really did need to sell for whatever reason. Perhaps a quick deal for lesser funds was worth it to them.
7) Youre describing something close to fraud - or, at the very least, something unscrupulous - with respect to the old biddy. Why? Because the roofer would be deemed to be a professional, whose opinion is deemed to carry additional authority and weight. Hence why the legal system poses additional duties of care on certain “experts” in certain situations. If the seller took this watch to a dealer and asked to sell it, the analogy is slightly better. But they didn’t - they listed it on eBay, the most widely viewed private sales platform in the world.

I’ll stop there, but the two situations you describe are wildly dissimilar and not logically connected.

I see zero issue in what happened. Two individuals freely consecrated a transaction both were satisfied with. Those that have a deep abiding issue with that really must be upset at the manner we’ve constructed our economic society - perhaps a commune would be a more suitable lifestyle.

I totally disagree but there will always be 2 sides of opinion on this.

I've noticed that in many cases with cal 321 Speedmasters' ads on eBay the title of the ad is not correctly describing the watch. For example last night this one sold for 6,6k USD: https://www.ebay.com/itm/Vintage-Pre-Moon-Landing-Omega-Speed-Master-Wrist-Watch-/114005950516
"Vintage Pre Moon Landing Omega Speed Master Wrist Watch"
It does not say the reference number and the spelling is wrong.
Considering the seller has plenty of experience it seems strange not to add ref.
So, is this some kind of strategy?

@Risto I'm not sure it's a strategy... I wish I could remember who it was on this forum (so I could give them credit) that mentioned they've had some great finds due to searching misspelled words in auction titles. And since reading that post, I myself have had two great non-watch-related auction finds/wins due to similar things. Seems not everyone thinks to put the details in the title or in this case, to run the words 'speed' and 'master' together. For my finds it was a misspelled word (one letter left out) and in the other case, the style name being left out with just more of a generic description of the item in its place. Agreed strange not to add the ref. here though, as it would bring in more traffic, one would think!

A deal were both parties are happy and agree to is the principle of a good deal.

Not predatory. The seller set the price not the buyer.

This actually is a strategy for some sellers. From personal experience I know of some ebay sellers (not watches though) who purposely make their listing sound like they are uneducated rubes, when in fact they are highly experienced dealers. Their reasoning is that they are going to attract lots of bidders hoping to take advantage of them. This creates a "buzz" by having lots of watchers as well as bidders bidding the item up. I'm not saying I approve, but it IS done.

I disagree that there necessarily needs to be two different opinions on this issue, but regardless, if we accept your argument that something problematic happened here, how do we solve the issue moving forward?

A willing seller sold to a willing buyer...

There will always be people that look to profit, pay less, or charge more in a market economy. Meaning we either need to change the fundamental nature of our economic system, have a 3rd party, independent entity supervise every transaction (the governement?), or simply ban any sort of transactional business. Saying everyone should act according to some sort of pious, unwritten moral code on all transactions simply isn't realistic or plausible - so you would need to formalize in some manner.

What do you propose?

Interesting... not a strategy I would think could work, at least not as well as including all the best searchable items in the auction title, but if it works, it works!

Such a healthy discussion. Experiences and knowledge shared in this thread are very informative and helpful.