Im not sure if this has been asked before, but the immense value of salt historicaly seemed to influence much policy of the time (specifically Rome). Why was this so valuable? Why would Roman soldiers even want a salary, if they could just head to the sea and get salt? What is the important thing that I am missing here?
And as an addition, when did salt become available enough to be considered a normal good?
There are no real evidence supporting the idea of excessive value of salt in late Roman Republic or early Empire. Sure, it was more expensive than today due to demand and either inefficient or costly methods of production (to obtain it by evaporation you require time and large pans that are an investment), but price of salt was nowhere near the cost of other spices or exotic goods. You can check the following threads for additional information:
https://www.reddit.com/r/AskHistorians/comments/9ffday/so_if_salt_was_a_currency_at_times_in_rome_are/ - This one discusses the veracity of the 'salt'-'salary' relation.
https://www.reddit.com/r/AskHistorians/comments/3zrjek/ive_got_30_tons_of_salt_and_im_in_210_bc_if_i/ - Here you can read more about the price of salt itself, take note of the responses by u/mormengil and u/XenophonTheAthenian
https://www.reddit.com/r/AskHistorians/comments/4kz3le/im_given_to_understand_that_in_the_premodern/d3ixfgr/ - Here you can find some information about technology of the early salt production.
https://www.reddit.com/r/AskHistorians/comments/3pnjcq/why_was_salt_so_important_in_trade_was_it_ever/ - And here, the question itself discusses the price of salt from Diocletian's edict (but this is late 3rd century CE, so it may be outside of your scope).