Back to the original topic.....
When I read the article I had quite a laugh. We have to remember that TAS serves an industry based on the simple assumption that spending more money gets you better sound. Anyone, even multimillionaires, want to think they are receiving good value for their money so the theory of "accelerating returns" fits right into the agenda.
I'm sure this idea has been floating around high-end showrooms for some time and the magazine decided to give it an aura of credibility. This idea is right out of the salesman's handbook. When you've got a customer that is willing to spend $500K why would you tell him that he could get just as good of sound for $300K? In the real world, the salesman's job is to convince that customer that spending $750K instead of $500K will bring a huge improvement in sound. If the poor guy cheaps-out and only spends $500K he will surely be disappointed because he could have had a system that was so much better. for an extra $250K.
The other factor to remember is that sound quality in high-end audio is only one factor in the buying decision. The appearance and story behind the gear is a key part of the buying decision but one of the most important elements of the sale is the relationship the salesman creates with the customer. The personal attention that one gets when spending several hundred thousand dollars on luxury goods is an enjoyable part of the process.
The marketing of luxury goods has a common thread in that the high cost of the item is actually a feature of the product. Exclusivity is a selling point. The idea that there is a accelerating improvement in performance with increasing price is a wonderful piece of sales propaganda. A commission salesman's wet dream.
When VPI introduced its top end turntable the Japanese distributor complained that the price was too low. Their customers wanted to spend more money than that and it didn't matter that the VPI would compete with six figure turntables.
After going to two audio shows (pre covid) I came to the conclusion that the correlation between sound quality and cost is tenuous at best. The best systems I heard were indeed expensive but I found no consistent pattern of high price leading to better sound.