Mine has never carried it for some reason...

Road or table?

table/canning

nope

4 lb box of Mortons is biggest mine carries.  And I've carried a LOT of them outta there

Couldn't you just buy the 40-lb bag of salt for water softening systems?  Or is there a difference for 'food grade' salt?

You can.

But honestly salt is cheap.  
Table salt usually is iodized, but you don’t want that for canning.  

Salt is pretty basic, like sugar, it does not require very special packaging.

We just store the 26oz. Morton containers in a watertight storage container and it keeps for years.  
We store the iodized/non-iodized/sea salt and boxes of canning salt.

feed stores carrry bags of stock salt also.

I bought Morton salt in 25 pound bags to store. From Amazon, the price has gone up since I bought it.
Salt

Local feed store sells Cargill in 40# bags.
Around $10 now though.

In the late '80s, I bought a TRUCK load, almost 22 tons, 540 80# bags.
Was just under $5 per bag back then

And our forklift wouldn't start...

I would think most grocery stores could order this in for you.  I am guessing it should run around $ 20.00 a 50 lb bag.  We sell it for $17.50 a bag by the skid., $ 18.98  by the individual bag.

Last year it was closer to $12.00



500 +bags by hand.  That would be both unpleasant and memorable.

Look for restaurant supply stores

Yes.  I have bought 25-lb bags of iodized salt from GFS.  I do not recall if noniodized was available.  But I did read Alas, Babylon, so I know the value of storing salt.  

It really comes down to how much salt you really think you will need.

How much to store would depend if you were planning for your own use as flavoring, you own use for curing / preserving, or your own use plus as a trade or exchange good to other people.

For your own use as a flavoring enhancer, a few bags would be plenty (and iodized would be fine).  If you are preserving your own meat & vegetables, you should have several more.  If you are trading your goods or services as a butcher & were curing meat, as well as trading butchering supplies (salt, casings [from animals you butchered], curing salts, etc...) ,  perhaps a few pallets of salt would suffice.  

If I for instance, if I wanted my garden turned over and I did not have the fuel or equipment to do it, perhaps I could trade 10 or 20 lbs of salt to my neighbor for his time & labor with his horse drawn plow.  Or a box of 22lr.  Or 10 lbs of nails, or a few dozen canning jar lids.  Or whatever I had extra of that he was in need of.

As a note: lots of people live in congested areas known as cities.  Cities have lots of stores where many products are stocked and sold.  Rural people do not have the option of lots of stores, and because of that they are more accustomed to trading with their neighbors.  What that means is your practical working relationship with your knowledgeable, skilled neighbors is going to directly affect you differently than those living in the cities.  The rural man that does his own butchering and has some supplies can count on being asked to help his neighbors with skilled labor and/or supplies during times of shortages.  If he has stocked up, he has the ability to better his life as well as his neighbors lives.  This is what I am referring to above in the part about trading your goods & services above.  A man living in a rural area should expect to be asked for his skilled labor by his neighbors and be prepared for it.

It depends on what you are planning for.  Nevertheless, salt is still inexpensive at this time relative to it's value.  That means it is still a good time to stock up on.

I don't see it online via Plus. Which, by the way, is very worth the price. For a lot of items you get them shipped free and for the same cost in store. Love it for bulk home and pantry staples

Before the China virus our Costco had 25 lbs bags all the time...

....then all supplies were diminished for months...

...when supplies started coming back, the salt never did at Costco, even as of now 2 1/2 yrs later.

Sometimes yes, sometimes no.
Their packaging and shipping leaves a lot to be desired.  I ordered two skids of 10 lb bags of sugar from them (2500 lbs each).  Instead of shipping 2 skids via freight truck so we could unload them at the dock, they sent 125 boxes via FedEx delivery truck, each box with 4 10lb bags in it.  There were many damaged boxes, sugar was spilling in streams from the delivery truck to the warehouse, where we had to inventory, clean up the mess, and restack on skids again.  The fedex driver was disgusted, we were annoyed, and based on how the boxes were packed, I believe the personal packing the boxed were upset while they were packing the boxes.  We didn't do that again with sugar, but based on store availability, we are still buying and shipping gallons of mayonnaise through them,  We can usually figure 10% to 20% damage, we take photos, they credit the damage, we clean up the mess.  It is a hassle, but it is our only option.  There is no way it can possibility be profitable for them to keep crediting this amount of loss, but since the local stores are constantly out of stock, our options are limited.