Couple things.
1) I use a full bag when I mix salt. It's essentially pre-measured, the bucket comes in a single bag.
2) Not having to measure ALL of the salt when I mix up a batch is worth well more than $0.80 to me
3) Every subscribe and save I have gotten from amazon comes as a solid rock, because they send all their old stock out via that ordering mechanism (not how Chewy works though)
4) The purpose of my comment was that calculating price based on BRS who sells everything based on MSRP is a bad metric
5) If you really need BAGS its about $10 cheaper to buy 4 bags than it is to buy 1 box of 4 bags