This debate (like most others of its ilk) is conflating three very different topics. The first and least relevant topic is price, hence all the discussion of gold plated cars and diamond studded dog collars. The second is performance which for most of us I think is more important. The third topic is value, i.e. the combination of price and performance.
It is unclear if the OP was questioning just the price of the Durand clamp ("no clamp, however high performing could be worth that much"), or challenging its performance ("all clamps sound the same"), or thirdly combining the two and challenging its value ("you can get the same result with my home made clamp")
If we focus on the performance question alone then the appropriate framework is to conduct a shootout as I did of a $50 Michell clamp, versus a $250 Oyaide clamp, versus the $3500K (less substantial discount) Durand. And yes to me the differences were clear.
Next question is then value -- was it worth an additional $2.5K for the improvement over the Oyaide, well in the context of my system, my pocketbook, and where else I could spend the same money it was.
So there we have it -- price never entered into it. If the clamp had been gold plated (but the same performance) and cost $5K instead of $3.5K the value discussion would be different