Okay, recently purchased some French Grey sea salt--"Esprit Du Sel" from the Island of Ré. I think this is a great salt--mild, almost sweet-ish, and brings out the best as a finishing salt...
Now I discover that this Grey salt is actually taken from the bottom of the salt marshes of this French Island (which is why it is grey in color--due to contact with the clay), and that the finery of these salt marshs, the white pristine salt from the top crust, the "Fleur du Sel", is another, and much more expensive, salt altogether--costing 5 times more than the "grey sludge" salt that I have...
Is the Fleur de Sel (specifically from Brittany's Island Ré--"Fleur de Sel de l'Ile de Ré") worth the high cost, the extra money over the "sludge" Grey salt? What's the difference between the more common grades of "Grey Salts" from the bottom of the marshes and the more elite "Fleur de Sel" taken from the top of the marsh? What flavor differences, palate subtleties, occur with these two different French grades of sea salts...?
Is it just hype and Euro marketing as some claim?
For everyday cooking and baking, I use regular table salt. A few special applications get Mexican Sal Gruesa del Mar---Coarse sea salt. It's tastier, due to the impurities. I think I once found traces of brine shrimp. That was tasty. What do you expect for 2 pesos a kilo?
I have some Sal Espuma del Mar from Colima which is very wonderful. Also have a kilo of sal de mar that I bought in Zitacuaro. It's a good all purpose salt but not as soft or mellow as the stuff from Colima. Check it out, you should be able to find both of these without too much difficulty, and as you've noted, it's dirt cheap.
There's a really great book on the history of salt by Mark Kurlansky (http://www.amazon.com/Salt-World-Hist...). I've read it twice now and am working on the history of sugar and other spices.
As for these specific salts, yes they will add flavor but some add unwanted flavor. No matter the price, if the salt is grayish brown that generally means it is dirty or impure. For thousands of years (especially the last 500 yrs) the whiter the salt, the more valuable it was. Fortunately, as the supply of white white salt has risen dramatically (both through empirical and scientific endeavors), the cost has dropped, and because not many produce salt by antiquated means, the supply of impure salt has dropped causing a rise in price. Sea salt often contains other minerals and the Fleur de Sel has a different crystalline structure due to the formation process.
To sum it up 200 years ago, the salt for which you're paying upwards of $20/lb used to be not worth it's weight in salt.
P.S. I'm a great fan of plain old coarse kosher salt for cooking and non-iodized morton's for baking (the iodine adds an unsavory metallic favor and the kosher has too big of crystals to spread evenly throughout a baked good).
I do not know about French salts. But I love salt. I try to buy sea salt every place I go (meaning vacations or interesting travels). I do small taste tests with food. It is fun to learn which I prefer with what food.
Salt has always being important. I recall a story of the Roman soldiers being paid in salt hence the word salary.
I figure if the expensive stuff is less than $20, why not go for it?