I think the shipping may have to do with them trying to clear out pool inventory.

If you buy at Amazon a lot, you can get no-extra cost 2-day shipping for a year for $85. (Amazon Prime). It has a 1 month free trial, so you can try it, and then cancel if it's not worthy it for you. For me, personally, it's VERY worth it in December, since I tend to be a put-it-off shopper!

Home Depot sells some KemTek and if you get the right stuff, there, it's fine. (In fact, there's nothing special about KemTek, except that they are big enough to have their own gooped-up blends so they still have to sell the basic chemicals.!)

Of course the cheapest pure dichlor that we know about is the PoolBrand stuff from Sams Club. (Costco is selling a gooped up blend!)