First, the Journal of Consumer Research published that credit card purchases have the power to change the way a buyer views his purchase. Simply because the card shifts the focus of the buyer to product benefits rather than cost. Paying in cash, on the other hand, focuses on the price to pay and not on why the product should be purchased.
Second, because the impact of the purchase is felt later, the illusion of scarcity is removed. So the buyer focuses on the perceived benefits. Paying in cash, on the one hand, would move the buyer to weigh the cost of the product against the benefit because once the money gets out of his hand, it is gone forever.