Interesting topic, @alexasuess, although reaching conclusions may be difficult (as @Elliot_Nesterman has pointed out).
I am no expert in the French jewelry market, but in the Spanish market there are two words used to describe personal adornment in the shape of jewelry: “bisutería” (that you would call “costume jewelry”) and “joyería” (fine jewelry); the term “alta joyería” (high jewelry") is also of common use (I think that this may be considered a convention throughout Europe).
Fine jewelry has been traditionally made of precious materials (this is precisely the reason for hallmarking): silver, gold, platinum (considering the permitted karatage for each country). On the opposite, [custome] jewelry is not made of precious materials (this is where plated base metals are of common use, for example); historically speaking, custom jewelry imitated fine jewelry (but it was much more affordable, which was the pursued objective).
The value of the so called contemporary jewelry pieces, theoretically, has nothing to do with its materials. In fact, the creators of contemporary jewelry have actively tried to avoid traditional precious materials for a long time. With reference to what might be considered “art”… well, that’s a different debate.
The way I see it, the difference between fine, bridge, and high jewelry depends on price ranges (that are defined by materials, craftmanship, brand, etc.). You may also add “demi-fine” jewelry to this list:
In any case, the boundaries have been becoming more and more blurred and you can easily find now branded costume jewelry that is much more expensive than non-branded fine jewelry, for example. In addition, it should be taken into consideration that the concept of “precious material” changes depending on culture and historical period (jade has been more valuable than diamonds in Asia, feathers of some bird species have been more valuable than gold in some Mesoamerican areas, etc.).
Just my two cents