It may very well be they are selling a such a low price, because it is a new store. Such prices may not be maintain.
My Leslies tends to have the sale on every month. Right now even on the tail end of the swim season I just got a mailer showing 2 for $7.98 2.5Gal Refills. They even do a 3 for $9.99 during the height of the summer. Plus they have a buy 10 get the 11th free punch card. Which if taken into account drops the price a bit more on average.