According to a water test at Leslie's, I needed 33 pounds of sodium bicarbonate (baking soda/soda ash) because my alkalinity was only 60 and should be 100. I wasn't sure how much sodium-bicarbonate I had at home so I didn't buy it at the time (Leslie's calls sodium-bicarbonate "Alkalinity Up."
I had only a few pounds so I checked Leslie's web site and they were charging $80 for 50 pounds . That seemed high to me for baking soda, so I called another pool store, and they charged $34.50 for 50 pounds (Arm and Hammer brand). It was about five miles away but we were going that direction anyway. Later I checked Costco's business warehouse on the web site and they charge $7.53 for 13.5 pounds, which would be $33.47 for 50 pounds, and the smaller bags would have been more convenient, but it was too far to go.
Another big difference is in the cost of phosphate removers. The dilution of the active ingredient varies tremendously so you can't go by volume. I bought a gallon of Orenda PR1000 (aka "BluePRO") for $130. It's painful to pay $130 for a gallon of anything, but PhosFree is about seven times as expensive that PR10000 for the equivalent phosphate removal.
For liquid chlorine, I pay $2.50/gallon for 12.5% strength in returnable bottles, while most stores, including Leslie's charge much more than that for 10% strength in a box of two. The Hasa chlorine in returnable bottles is also much fresher as it's delivered every two days from the manufacturing plant, and doesn't sit around in a hot storage facility.