Wrong pricing

Yesterday, my brother asked me to go and him a pair of chinos for a function that is next weekend and courier it to him because he is in a small town where there are less options. he had a less budget but I promised to get something decent for him. When I got to Woolworths fourways mall, I saw what I liked for him which was R200 more than his budget, but because I liked it, I took it upon myself to convince him to get it, which he agreed and sent me the money, when I went back for the size I told that it was actually the wrong price that was on the item and the actual price was R200 more than what was on the item, I actually told the guy that the exact amount has already been sent and I should be given that item with that amount, which he disagreed with me, I ended up having to fork out that R200 from my pocket because I already convinced him to get it which I believe that it is not fair for a customer to pay for your mistake...........