Yikes, your link has the Waterbob sale priced at $30.
Here, CTD has ‘em in stock for half that:
http://www.cheaperthandirt.com/product/CAMP-20
Normally, I found, when hurricane season starts, the bags sell out. I'll use the Cheaper Than Dirt link from now on, plus a poster said Amazon has them for $20.60 and if you are a Prime member there, shipping is free. I'll use that link from now on, too, if they remain on Amazon and that goes for Cheaper Than Dirt, too.