Experience with countertop basins?

The design will not be the same for the connoisseur and the expert.

Yes, of course, this possible explanation also exists. By the way, with door handles in the same way as with washbasin faucets.

This is the "secret" of the business of product piracy: that a brake disc for a tenth of the original manufacturing price only reveals under the microscope where the price difference comes from

On the other hand, there are indeed always things where only the price is really higher ...

Ok, but with a brake disc I can already sensibly explain the difference. Both may look the same. However, the behavior under heat/stress is often very different.

But how is it with a fitting? What "can" it do differently than the other? Does it last longer? Is it more resistant to "harsh" cleaning agents? Or or or... How is the "added value" argued here? (Is it even?)

What justifies the higher price?

Quite simple; supply and demand!

Axor also has a faucet where the designer was inspired by two different streams flowing together when designing it. That must be worth hundreds of euros to the dear buyer as well.

Why is a Kandinsky worth more than a painting by Uncle H, who has also been painting passionately and well for decades?

At the plumbing dealer, we saw the faucet series Grohe Essence. In matte, it seems very stylish to us. However, the installer said that he would not use it in an area with hard water, as such brushed items are very susceptible to limescale. Even with a water softener system that we install, we wouldn’t manage it. Do you see it the same way?

...
But how does it behave with a fitting? What can it "do" differently than the other? Does it last longer? Is it less sensitive to "harsh" cleaning agents? Or or or... How is the "added value" argued here? (Is it even argued at all?)

It may well be that on very cheap fittings the shiny coating flakes off. There is also material that constantly looks dirty because water spots or fats/proteins (from fingertips) leave marks.
However, with solid manufacturers, this should not be the case.

Basically, you can assume that faucets from brand manufacturers, which are also used for non-private properties, are always technically durable and have lasting chrome plating. Thus, we have, not only in new buildings but also in the office, faucets from the company Ideal, whose toilets Ideal Standard have gained a certain fame. We can assume that the faucets will do what they are supposed to do for years without losing their chrome. They just don’t look “designed,” but simply look like single-lever mixers usually do. In the kitchen, we have a no-name faucet from Ikea, which they advertise with a 10-year warranty. Let’s see, I will report in 2027 how it has performed, if I am still able to write then. Karsten