PVR Cinemas — about beverages

Have been to pvr cinemas in irrum mamzil and brought zago cold coffee which costs 150 rupees for 250 ml. I know the mrp is 150/- but why the special price for the theatres when it only costs 70/- for 250 ml outside. I have checked and amazon and few other sites and it is 420rs for pack of 6. Why it is overpriced in pvr cinemas
Not only this all the food available there is overpriced.