Trying to solve dishwasher tab math.

So the 115 box I bought at Wal-Mart awhile back(fairly certain). And the 105 box was today from Canadian Tire. The Walmart box says that it provided the extra tabs at no extra charge to the supplier. Then the other box is 30% more then the box I bought?? In my quick search around every store has a difference size (Costco 140 units) and there's really no other competition in the market for this particular product. Specifically dishwasher tabs that are pressed powder.