A few of thoughts on this:
-Seat maps aren't a good indicator of how many tickets remain. Those of us who are obsessive about things like seat selection may find it hard to imagine, but there are just as many (or more) people totally blase about it. There are ways to look up real inventory—ExpertFlier is the best for that—but they're limited without paying for a subscription.
-There are consolidators, ticket brokers, cruise lines, and tour companies that might sell a price without an itinerary, and only confirm the itinerary closer in. (The underside of these look like trading options on futures.) If you've ever seen a cruise or tour that promotes "air included" or "$300 business class air" if could be this kind of deal. Note that while this is a 'third party booking', it's quite different from buying on Expedia or CheapoAir.
-Lastly... Yes, some people are paying those prices. Well, their companies are. It's been slow to return after Covid, but business travel is back,. Seat-miles for business travel are somewhere over 75% of pre-Covid levels while revenue is somewhere around 85%.