As anyone who has ever bought something from the iTunes Store has probably noticed, Apple doesn't email you the receipt for your purchases immediately after your transaction is complete. In fact, if you've ever looked closely at your bank statement for your iTunes purchases, you may have noticed that the cost of your purchase isn't actually charged to your account for a period - a couple of hours to a couple of days - after your purchase is complete.
A store not actually taking your money at the time it gives you your purchase is a little bit unusual. So what gives: why the delay in iTunes Store billing?
The answer, it turns out, has to do with user behavior and, most importantly, credit card fees.
Most credit card processors charge their clients both a per-transaction (or sometimes monthly) fee and a percentage of the purchase they're processing. On a big ticket item - say an iPhone or a new laptop - the retailer can absorb these fees without much trouble. But, for a very small payment - say US$0.69, $0.99, or $1.29, the cost of individual songs at iTunes - it becomes harder to make money if you charge a credit card each time someone buys a single song. If you were to do that, the iTunes Store would drown in a sea of fees and one-off charges, making profitability all the more difficult.
However, user behavior is such that when you buy a single song or album from the iTunes Store, it's likely that you're going to buy another - often pretty soon after. And that's why Apple delays its billing. It's betting that users will make additional purchases at the iTunes Store and then instead of charging $0.99 to your credit card, they can charge, for instance, $10.98 (the cost of the one song you bought one day and the album you bought the next day), which is an amount easier to derive profit from.
It doesn't always work, of course - lots of people don't make numerous purchases spread out over a few days - but apparently it works often enough for the strategy to be effective for Apple.
