What do I do if iTunes charged me too much?

I bought an album whose regular price was $10.99 but was on sale for $8.41. When I went to buy it (I was sending it as a gift to someone), it charged me the full $10.99. How do I get Apple to refund the difference. I realize it is a small amount of money but it is the principle of the thing (and the small amount of money!).