Human nature: When someone pays a lot of money for something that is touted to be 'great', they dont want to admit to themselves that it is no better than the other stuff. Placebo effect.

Fin design is so refined now that there is so little difference between fins in the same category that those differences become insignificant on their own.
It is far more significant and advantageous to find a fin, board and rig combination that suits your particular situation. Venue, wind conditions, water conditions, personal style of sailing preferences. etc. Some boards just like some fins and not others, no matter how expensive or 'high tech' they are. Tuning your sail and rig can greatly affect how your fin behaves. The list goes on.
The 'fastest fin' does not exist. What is best for you, or fastest for you, changes evry time the conditions and your equipment changes, and even with your metal outlook.
There are practical considerations and limitations like, weed, shallowness, sand or rocky bottom and potential to wreck the fin, the particular character of the shop, waves ot lack thereof where you sail, etc, and of course the cost of a fin. The latter is a very real consideration because it can facilitate or limit your ability to try different fins and combinations to find the best setup in constantly changing and evolving circumstances.
Horses for courses.