Seth's Blog: What people buy when they buy something on sale | Psychology of Consumer Behaviour |

Assuming it's not something they were shopping for in the first place... The impulse big-sale buy is not a matter of acquiring a high value item they'll need later at a bargain price today. No, the consumer is spending money in exchange for the feeling, right now, of saving big. The joy of a bargain. The item is secondary, the feeling is what we just paid for."