Say you are selling bags of popcorn for £1.50, and 60 people buy some. That makes £90.
People typically buy snacks at halftime, as well as when the price is low.
If you lower your price to £1 a bag, and double the amount of people buy it, you make £120.
If you cut the price by a third, and more people buy it, you should, in theory, break even or make more profit.
I would price my popcorn as half the price as they sell at the store I would do this because then you will be making more money then the store because you will get more customers.