Anyway, the caveat emptor or buyer beware angle is make sure you are paying attention at the check out when the goods are being scanned.
I picked up some tuna in a can (Greenseas) and some Schweppes Bitter Lemon. Now, I am pretty good at knowing when stuff is cheap or on special. My mum has taught me well. Once I had gone through the check out and paid using the trusty old credit card. I thought the bill seemed a little expensive but still around where I thought it might be. I checked the print out and the tuna was more than 7,000 rupes more than the tag on the shelf and the bitter lemon was more than 2,000 more expensive than the advertised price. By this stage I was already in the taxi and getting ready to make a b-line home.
The moral of this story -- stay aware!