Usave Tarkastad EC

Usave Tarkastad - I bought a 2.25L coke, the zero caffeine zero sugar. Recommended retail price is R18 but paid R21.99. When enquired from the Manager she advised that it is coca cola price not theirs. How much extra have they been making from all customers who have been buying the coke from their stores. What was the deal that was made between them and Coca cola when they agreed to sell the product from their stores.