They can, of course, always repeat the post-match discounts they were previously offering. Stuff like a quid of the price of pie, for everyone. Or free beer if Ashley Barnes scores a hat-trick. Whatever they fancy on the day. The card discount pales into insignificance with that sort of deal.
Here's a question from a university microeconomics exam paper:-
The owner of a football club has access to the following information about elasticities of demand for tickets:
Own price elasticity 1.4
Income elasticity 1.8
Cross-elasticity with respect to meat pies at half time -1.1
a. What...
Simple economics will tell you that price elasticities kick in. Charging more at half time will reduce demand. Depending on the value of the elasticity, it could even reduce sales income. It should be relatively easy to check the sales and revenue data after a few weeks, though, and make...