I have heard that Roman soldiers were paid in Salt, and we still have phrases like a man "worth his salt". In ritualism around the world as well, salt also seems represent something rather valuable.

My basic understanding is that Salt was a precious commodity in Ancient times, was valuable during the height of the Spice Trade, and then became mundane in modern times.

So what happened to change that, and when?

Was Salt ever particularly valuable?

(Yes, I'm sure its a large global industry so its not exactly "devauled", but my understanding is that it certainly used to be much more valuable per pound)

Thanks!