It’s about thermal storage, you don’t use table/sea salt for that, and you don’t need a lot of salt, because the salt is in a closed loop; it’s not being consumed.
But more thermal storage you want more salt you want, and it's gotta cost something, right?
If you read the article you sent me, you'll learn that, just as I said, you don't use sodium chloride, aka table salt, aka sea salt, for these purposes.
A better example are sodium ion batteries, which are about to take off in a big way