I'm stocking up on sodium bicarbonate (aka baking soda) this year. It seems the cheapest option, by far are 13.5lb Arm & Hammer bags at Sams Club for $6.88 a bag. I'm surprised pool stores aren't even competitive with this price, it's nearly 3x the price at a pool store, for the same store. In fact, Sams club sells the same stuff in their pool section at the higher price. I know it's the same stuff, just different names.
Anyone know how to explain the markup here?